diff --git a/src/globals.h b/src/globals.h
index 49a6266de..cdaa2ed06 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -123,16 +123,16 @@ extern void jerry_ref_unused_variables (int unused_variables_follow, ...);
     jerry_unreachable (NULL, __FILE__, __FUNCTION__, __LINE__); \
   } while (0)
 
-#define JERRY_UNIMPLEMENTED() \
+#define JERRY_UNIMPLEMENTED(comment) \
   do \
   { \
-    jerry_unimplemented (NULL, __FILE__, __FUNCTION__, __LINE__); \
+    jerry_unimplemented (comment, __FILE__, __FUNCTION__, __LINE__); \
   } while (0)
 
-#define JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(...) \
+#define JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(comment, ...) \
   do \
   { \
-    jerry_unimplemented (NULL, __FILE__, __FUNCTION__, __LINE__); \
+    jerry_unimplemented (comment, __FILE__, __FUNCTION__, __LINE__); \
     if (false) \
     { \
       jerry_ref_unused_variables (0, __VA_ARGS__); \
@@ -145,16 +145,16 @@ extern void jerry_ref_unused_variables (int unused_variables_follow, ...);
     jerry_unreachable (NULL, NULL, NULL, 0); \
   } while (0)
 
-#define JERRY_UNIMPLEMENTED() \
+#define JERRY_UNIMPLEMENTED(comment) \
   do \
   { \
-    jerry_unimplemented (NULL, NULL, NULL, 0); \
+    jerry_unimplemented (comment, NULL, NULL, 0); \
   } while (0)
 
-#define JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(...) \
+#define JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(comment, ...) \
   do \
   { \
-    jerry_unimplemented (NULL, NULL, NULL, 0); \
+    jerry_unimplemented (comment, NULL, NULL, 0); \
     if (false) \
     { \
       jerry_ref_unused_variables (0, __VA_ARGS__); \
diff --git a/src/libcoreint/interpreter.c b/src/libcoreint/interpreter.c
index 48bdafad0..3ce738cad 100644
--- a/src/libcoreint/interpreter.c
+++ b/src/libcoreint/interpreter.c
@@ -439,7 +439,7 @@ run_int_loop (int_data_t *int_data)
     if (completion.type == ECMA_COMPLETION_TYPE_BREAK
         || completion.type == ECMA_COMPLETION_TYPE_CONTINUE)
     {
-      JERRY_UNIMPLEMENTED ();
+      JERRY_UNIMPLEMENTED ("break and continue on labels are not supported.");
 
       continue;
     }
diff --git a/src/libcoreint/opcodes-native-call.c b/src/libcoreint/opcodes-native-call.c
index 73e3c08c9..bd72fc5d7 100644
--- a/src/libcoreint/opcodes-native-call.c
+++ b/src/libcoreint/opcodes-native-call.c
@@ -141,7 +141,7 @@ opfunc_native_call (opcode_t opdata, /**< operation data */
 #if CONFIG_ECMA_CHAR_ENCODING == CONFIG_ECMA_CHAR_ASCII
         __printf ("%s\n", (char*) zt_str_p);
 #elif CONFIG_ECMA_CHAR_ENCODING == CONFIG_ECMA_CHAR_UTF16
-        JERRY_UNIMPLEMENTED ();
+        JERRY_UNIMPLEMENTED ("UTF-16 support is not implemented.");
 #endif /* CONFIG_ECMA_CHAR_ENCODING == CONFIG_ECMA_CHAR_UTF16 */
 
         mem_heap_free_block (zt_str_p);
diff --git a/src/libecmabuiltins/ecma-builtin-array-prototype-object.c b/src/libecmabuiltins/ecma-builtin-array-prototype-object.c
index 768765484..bfe1330c4 100644
--- a/src/libecmabuiltins/ecma-builtin-array-prototype-object.c
+++ b/src/libecmabuiltins/ecma-builtin-array-prototype-object.c
@@ -89,7 +89,7 @@ const ecma_length_t ecma_builtin_array_prototype_property_number = (sizeof (ecma
 static ecma_completion_value_t
 ecma_builtin_array_prototype_object_to_string (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_array_prototype_object_to_string */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-function-object.c b/src/libecmabuiltins/ecma-builtin-function-object.c
index 812c338ae..ffef3acbc 100644
--- a/src/libecmabuiltins/ecma-builtin-function-object.c
+++ b/src/libecmabuiltins/ecma-builtin-function-object.c
@@ -236,11 +236,7 @@ ecma_builtin_function_dispatch_construct (ecma_value_t *arguments_list_p, /**< a
 {
   JERRY_ASSERT (arguments_list_len == 0 || arguments_list_p != NULL);
 
-#ifdef CONFIG_ECMA_COMPACT_PROFILE
-  return ecma_make_throw_obj_completion_value (ecma_builtin_get (ECMA_BUILTIN_ID_COMPACT_PROFILE_ERROR));
-#else /* !CONFIG_ECMA_COMPACT_PROFILE */
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arguments_list_p, arguments_list_len);
-#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arguments_list_p, arguments_list_len);
 } /* ecma_builtin_function_dispatch_construct */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-function-prototype-object.c b/src/libecmabuiltins/ecma-builtin-function-prototype-object.c
index 499adfa82..f8daa5712 100644
--- a/src/libecmabuiltins/ecma-builtin-function-prototype-object.c
+++ b/src/libecmabuiltins/ecma-builtin-function-prototype-object.c
@@ -97,7 +97,7 @@ const ecma_length_t ecma_builtin_function_prototype_property_number = (sizeof (e
 static ecma_completion_value_t
 ecma_builtin_function_prototype_object_to_string (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_function_prototype_object_to_string */
 
 /**
@@ -114,7 +114,7 @@ ecma_builtin_function_prototype_object_apply (ecma_value_t this, /**< this argum
                                               ecma_value_t arg1, /**< first argument */
                                               ecma_value_t arg2) /**< second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_function_prototype_object_apply */
 
 /**
@@ -131,7 +131,7 @@ ecma_builtin_function_prototype_object_call (ecma_value_t this, /**< this argume
                                              ecma_value_t *arguments_list_p, /**< list of arguments */
                                              ecma_length_t arguments_number) /**< number of arguments */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arguments_list_p, arguments_number);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arguments_list_p, arguments_number);
 } /* ecma_builtin_function_prototype_object_call */
 
 /**
@@ -148,7 +148,7 @@ ecma_builtin_function_prototype_object_bind (ecma_value_t this, /**< this argume
                                              ecma_value_t *arguments_list_p, /**< list of arguments */
                                              ecma_length_t arguments_number) /**< number of arguments */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arguments_list_p, arguments_number);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arguments_list_p, arguments_number);
 } /* ecma_builtin_function_prototype_object_bind */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-global-object.c b/src/libecmabuiltins/ecma-builtin-global-object.c
index 306c88883..69893ec05 100644
--- a/src/libecmabuiltins/ecma-builtin-global-object.c
+++ b/src/libecmabuiltins/ecma-builtin-global-object.c
@@ -93,13 +93,7 @@ JERRY_STATIC_ASSERT (sizeof (ecma_builtin_global_property_names) > sizeof (void*
 static ecma_completion_value_t
 ecma_builtin_global_object_eval (ecma_value_t x) /**< routine's first argument */
 {
-#ifdef CONFIG_ECMA_COMPACT_PROFILE
-  (void) x;
-
-  return ecma_make_throw_obj_completion_value (ecma_builtin_get (ECMA_BUILTIN_ID_COMPACT_PROFILE_ERROR));
-#else /* !CONFIG_ECMA_COMPACT_PROFILE */
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (x);
-#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (x);
 } /* ecma_builtin_global_object_eval */
 
 /**
@@ -115,7 +109,7 @@ static ecma_completion_value_t
 ecma_builtin_global_object_parse_int (ecma_value_t string, /**< routine's first argument */
                                       ecma_value_t radix) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (string, radix);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (string, radix);
 } /* ecma_builtin_global_object_parse_int */
 
 /**
@@ -130,7 +124,7 @@ ecma_builtin_global_object_parse_int (ecma_value_t string, /**< routine's first
 static ecma_completion_value_t
 ecma_builtin_global_object_parse_float (ecma_value_t string) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (string);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (string);
 } /* ecma_builtin_global_object_parse_float */
 
 /**
@@ -202,7 +196,7 @@ ecma_builtin_global_object_is_finite (ecma_value_t arg) /**< routine's first arg
 static ecma_completion_value_t
 ecma_builtin_global_object_decode_uri (ecma_value_t encoded_uri) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (encoded_uri);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (encoded_uri);
 } /* ecma_builtin_global_object_decode_uri */
 
 /**
@@ -217,7 +211,7 @@ ecma_builtin_global_object_decode_uri (ecma_value_t encoded_uri) /**< routine's
 static ecma_completion_value_t
 ecma_builtin_global_object_decode_uri_component (ecma_value_t encoded_uri_component) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (encoded_uri_component);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (encoded_uri_component);
 } /* ecma_builtin_global_object_decode_uri_component */
 
 /**
@@ -232,7 +226,7 @@ ecma_builtin_global_object_decode_uri_component (ecma_value_t encoded_uri_compon
 static ecma_completion_value_t
 ecma_builtin_global_object_encode_uri (ecma_value_t uri) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (uri);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (uri);
 } /* ecma_builtin_global_object_encode_uri */
 
 /**
@@ -247,7 +241,7 @@ ecma_builtin_global_object_encode_uri (ecma_value_t uri) /**< routine's first ar
 static ecma_completion_value_t
 ecma_builtin_global_object_encode_uri_component (ecma_value_t uri_component) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (uri_component);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (uri_component);
 } /* ecma_builtin_global_object_encode_uri_component */
 
 /**
@@ -564,7 +558,6 @@ ecma_builtin_global_try_to_instantiate_property (ecma_object_t *obj_p, /**< obje
 #ifdef CONFIG_ECMA_COMPACT_PROFILE
       /* The object throws CompactProfileError upon invocation */
       ecma_object_t *get_set_p = ecma_builtin_get (ECMA_BUILTIN_ID_COMPACT_PROFILE_ERROR);
-      ecma_gc_update_may_ref_younger_object_flag_by_object (obj_p, get_set_p);
       ecma_property_t *compact_profile_thrower_property_p = ecma_create_named_accessor_property (obj_p,
                                                                                                  prop_name_p,
                                                                                                  get_set_p,
@@ -574,9 +567,11 @@ ecma_builtin_global_try_to_instantiate_property (ecma_object_t *obj_p, /**< obje
       ecma_deref_object (get_set_p);
 
       return compact_profile_thrower_property_p;
+#else /* CONFIG_ECMA_COMPACT_PROFILE */
+      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
 #endif /* CONFIG_ECMA_COMPACT_PROFILE */
 
-      JERRY_UNIMPLEMENTED ();
+      JERRY_UNREACHABLE ();
     }
 
     default:
diff --git a/src/libecmabuiltins/ecma-builtin-math-object.c b/src/libecmabuiltins/ecma-builtin-math-object.c
index f01d0f7f6..d29fcc466 100644
--- a/src/libecmabuiltins/ecma-builtin-math-object.c
+++ b/src/libecmabuiltins/ecma-builtin-math-object.c
@@ -200,7 +200,7 @@ ecma_builtin_math_object_abs (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_acos (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_acos */
 
 /**
@@ -215,7 +215,7 @@ ecma_builtin_math_object_acos (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_asin (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_asin */
 
 /**
@@ -230,7 +230,7 @@ ecma_builtin_math_object_asin (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_atan (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_atan */
 
 /**
@@ -246,7 +246,7 @@ static ecma_completion_value_t
 ecma_builtin_math_object_atan2 (ecma_value_t arg1, /**< first routine's argument */
                                 ecma_value_t arg2) /**< second routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg1, arg2);
 } /* ecma_builtin_math_object_atan2 */
 
 /**
@@ -261,7 +261,7 @@ ecma_builtin_math_object_atan2 (ecma_value_t arg1, /**< first routine's argument
 static ecma_completion_value_t
 ecma_builtin_math_object_ceil (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_ceil */
 
 /**
@@ -276,7 +276,7 @@ ecma_builtin_math_object_ceil (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_cos (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_cos */
 
 /**
@@ -344,7 +344,7 @@ ecma_builtin_math_object_exp (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_floor (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_floor */
 
 /**
@@ -927,7 +927,7 @@ ecma_builtin_math_object_round (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_sin (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_sin */
 
 /**
@@ -994,7 +994,7 @@ ecma_builtin_math_object_sqrt (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_math_object_tan (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_math_object_tan */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-number-prototype-object.c b/src/libecmabuiltins/ecma-builtin-number-prototype-object.c
index dc0b2d696..04ecd9072 100644
--- a/src/libecmabuiltins/ecma-builtin-number-prototype-object.c
+++ b/src/libecmabuiltins/ecma-builtin-number-prototype-object.c
@@ -146,7 +146,7 @@ ecma_builtin_number_prototype_object_to_string (ecma_value_t this, /**< this arg
     return ecma_make_normal_completion_value (ecma_make_string_value (ret_str_p));
   }
   {
-    JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arguments_list_p);
+    ECMA_BUILTIN_CP_UNIMPLEMENTED (arguments_list_p);
   }
 } /* ecma_builtin_number_prototype_object_to_string */
 
@@ -217,7 +217,7 @@ static ecma_completion_value_t
 ecma_builtin_number_prototype_object_to_fixed (ecma_value_t this, /**< this argument */
                                                ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_number_prototype_object_to_fixed */
 
 /**
@@ -233,7 +233,7 @@ static ecma_completion_value_t
 ecma_builtin_number_prototype_object_to_exponential (ecma_value_t this, /**< this argument */
                                                      ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_number_prototype_object_to_exponential */
 
 /**
@@ -249,7 +249,7 @@ static ecma_completion_value_t
 ecma_builtin_number_prototype_object_to_precision (ecma_value_t this, /**< this argument */
                                                    ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_number_prototype_object_to_precision */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-object-object.c b/src/libecmabuiltins/ecma-builtin-object-object.c
index 6fdc7de6c..ae12f0ea3 100644
--- a/src/libecmabuiltins/ecma-builtin-object-object.c
+++ b/src/libecmabuiltins/ecma-builtin-object-object.c
@@ -181,7 +181,7 @@ ecma_builtin_object_dispatch_construct (ecma_value_t *arguments_list_p, /**< arg
 static ecma_completion_value_t
 ecma_builtin_object_object_get_prototype_of (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_get_prototype_of */
 
 /**
@@ -196,7 +196,7 @@ ecma_builtin_object_object_get_prototype_of (ecma_value_t arg) /**< routine's ar
 static ecma_completion_value_t
 ecma_builtin_object_object_get_own_property_names (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_get_own_property_names */
 
 /**
@@ -211,7 +211,7 @@ ecma_builtin_object_object_get_own_property_names (ecma_value_t arg) /**< routin
 static ecma_completion_value_t
 ecma_builtin_object_object_seal (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_seal */
 
 /**
@@ -226,7 +226,7 @@ ecma_builtin_object_object_seal (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_object_object_freeze (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_freeze */
 
 /**
@@ -241,7 +241,7 @@ ecma_builtin_object_object_freeze (ecma_value_t arg) /**< routine's argument */
 static ecma_completion_value_t
 ecma_builtin_object_object_prevent_extensions (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_prevent_extensions */
 
 /**
@@ -256,7 +256,7 @@ ecma_builtin_object_object_prevent_extensions (ecma_value_t arg) /**< routine's
 static ecma_completion_value_t
 ecma_builtin_object_object_is_sealed (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_is_sealed */
 
 /**
@@ -271,7 +271,7 @@ ecma_builtin_object_object_is_sealed (ecma_value_t arg) /**< routine's argument
 static ecma_completion_value_t
 ecma_builtin_object_object_is_frozen (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_is_frozen */
 
 /**
@@ -286,7 +286,7 @@ ecma_builtin_object_object_is_frozen (ecma_value_t arg) /**< routine's argument
 static ecma_completion_value_t
 ecma_builtin_object_object_is_extensible (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_is_extensible */
 
 /**
@@ -301,7 +301,7 @@ ecma_builtin_object_object_is_extensible (ecma_value_t arg) /**< routine's argum
 static ecma_completion_value_t
 ecma_builtin_object_object_keys (ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg);
 } /* ecma_builtin_object_object_keys */
 
 /**
@@ -317,7 +317,7 @@ static ecma_completion_value_t
 ecma_builtin_object_object_get_own_property_descriptor (ecma_value_t arg1, /**< routine's first argument */
                                                         ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg1, arg2);
 } /* ecma_builtin_object_object_get_own_property_descriptor */
 
 /**
@@ -333,7 +333,7 @@ static ecma_completion_value_t
 ecma_builtin_object_object_create (ecma_value_t arg1, /**< routine's first argument */
                                    ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg1, arg2);
 } /* ecma_builtin_object_object_create */
 
 /**
@@ -349,7 +349,7 @@ static ecma_completion_value_t
 ecma_builtin_object_object_define_properties (ecma_value_t arg1, /**< routine's first argument */
                                               ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (arg1, arg2);
 } /* ecma_builtin_object_object_define_properties */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-object-prototype-object.c b/src/libecmabuiltins/ecma-builtin-object-prototype-object.c
index 8b3e9f313..2520f4f7d 100644
--- a/src/libecmabuiltins/ecma-builtin-object-prototype-object.c
+++ b/src/libecmabuiltins/ecma-builtin-object-prototype-object.c
@@ -204,7 +204,7 @@ ecma_builtin_object_prototype_object_value_of (ecma_value_t this) /**< this argu
 static ecma_completion_value_t
 ecma_builtin_object_prototype_object_to_locale_string (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_object_prototype_object_to_locale_string */
 
 /**
@@ -220,7 +220,7 @@ static ecma_completion_value_t
 ecma_builtin_object_prototype_object_has_own_property (ecma_value_t this, /**< this argument */
                                                        ecma_value_t arg) /**< first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_object_prototype_object_has_own_property */
 
 /**
@@ -236,7 +236,7 @@ static ecma_completion_value_t
 ecma_builtin_object_prototype_object_is_prototype_of (ecma_value_t this, /**< this argument */
                                                       ecma_value_t arg) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_object_prototype_object_is_prototype_of */
 
 /**
@@ -252,7 +252,7 @@ static ecma_completion_value_t
 ecma_builtin_object_prototype_object_property_is_enumerable (ecma_value_t this, /**< this argument */
                                                              ecma_value_t arg) /**< routine's first argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_object_prototype_object_property_is_enumerable */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtin-string-prototype-object.c b/src/libecmabuiltins/ecma-builtin-string-prototype-object.c
index 9316755e5..aaef2a964 100644
--- a/src/libecmabuiltins/ecma-builtin-string-prototype-object.c
+++ b/src/libecmabuiltins/ecma-builtin-string-prototype-object.c
@@ -211,7 +211,7 @@ static ecma_completion_value_t
 ecma_builtin_string_prototype_object_char_at (ecma_value_t this, /**< this argument */
                                               ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_string_prototype_object_char_at */
 
 /**
@@ -227,7 +227,7 @@ static ecma_completion_value_t
 ecma_builtin_string_prototype_object_char_code_at (ecma_value_t this, /**< this argument */
                                                    ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_string_prototype_object_char_code_at */
 
 /**
@@ -244,7 +244,7 @@ ecma_builtin_string_prototype_object_concat (ecma_value_t this, /**< this argume
                                              ecma_value_t* argument_list_p, /**< arguments list */
                                              ecma_length_t arguments_number) /**< number of arguments */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, argument_list_p, arguments_number);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, argument_list_p, arguments_number);
 } /* ecma_builtin_string_prototype_object_concat */
 
 /**
@@ -261,7 +261,7 @@ ecma_builtin_string_prototype_object_index_of (ecma_value_t this, /**< this argu
                                                ecma_value_t arg1, /**< routine's first argument */
                                                ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_string_prototype_object_index_of */
 
 /**
@@ -278,7 +278,7 @@ ecma_builtin_string_prototype_object_last_index_of (ecma_value_t this, /**< this
                                                     ecma_value_t arg1, /**< routine's first argument */
                                                     ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_string_prototype_object_last_index_of */
 
 /**
@@ -294,7 +294,7 @@ static ecma_completion_value_t
 ecma_builtin_string_prototype_object_locale_compare (ecma_value_t this, /**< this argument */
                                                      ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_string_prototype_object_locale_compare */
 
 /**
@@ -310,7 +310,7 @@ static ecma_completion_value_t
 ecma_builtin_string_prototype_object_match (ecma_value_t this, /**< this argument */
                                             ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_string_prototype_object_match */
 
 /**
@@ -327,7 +327,7 @@ ecma_builtin_string_prototype_object_replace (ecma_value_t this, /**< this argum
                                               ecma_value_t arg1, /**< routine's first argument */
                                               ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_string_prototype_object_replace */
 
 /**
@@ -343,7 +343,7 @@ static ecma_completion_value_t
 ecma_builtin_string_prototype_object_search (ecma_value_t this, /**< this argument */
                                              ecma_value_t arg) /**< routine's argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg);
 } /* ecma_builtin_string_prototype_object_search */
 
 /**
@@ -360,7 +360,7 @@ ecma_builtin_string_prototype_object_slice (ecma_value_t this, /**< this argumen
                                             ecma_value_t arg1, /**< routine's first argument */
                                             ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_string_prototype_object_slice */
 
 /**
@@ -377,7 +377,7 @@ ecma_builtin_string_prototype_object_split (ecma_value_t this, /**< this argumen
                                             ecma_value_t arg1, /**< routine's first argument */
                                             ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_string_prototype_object_split */
 
 /**
@@ -394,7 +394,7 @@ ecma_builtin_string_prototype_object_substring (ecma_value_t this, /**< this arg
                                                 ecma_value_t arg1, /**< routine's first argument */
                                                 ecma_value_t arg2) /**< routine's second argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this, arg1, arg2);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this, arg1, arg2);
 } /* ecma_builtin_string_prototype_object_substring */
 
 /**
@@ -409,7 +409,7 @@ ecma_builtin_string_prototype_object_substring (ecma_value_t this, /**< this arg
 static ecma_completion_value_t
 ecma_builtin_string_prototype_object_to_lower_case (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_string_prototype_object_to_lower_case */
 
 /**
@@ -424,7 +424,7 @@ ecma_builtin_string_prototype_object_to_lower_case (ecma_value_t this) /**< this
 static ecma_completion_value_t
 ecma_builtin_string_prototype_object_to_locale_lower_case (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_string_prototype_object_to_locale_lower_case */
 
 /**
@@ -439,7 +439,7 @@ ecma_builtin_string_prototype_object_to_locale_lower_case (ecma_value_t this) /*
 static ecma_completion_value_t
 ecma_builtin_string_prototype_object_to_upper_case (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_string_prototype_object_to_upper_case */
 
 /**
@@ -454,7 +454,7 @@ ecma_builtin_string_prototype_object_to_upper_case (ecma_value_t this) /**< this
 static ecma_completion_value_t
 ecma_builtin_string_prototype_object_to_locale_upper_case (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_string_prototype_object_to_locale_upper_case */
 
 /**
@@ -469,7 +469,7 @@ ecma_builtin_string_prototype_object_to_locale_upper_case (ecma_value_t this) /*
 static ecma_completion_value_t
 ecma_builtin_string_prototype_object_trim (ecma_value_t this) /**< this argument */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS (this);
+  ECMA_BUILTIN_CP_UNIMPLEMENTED (this);
 } /* ecma_builtin_string_prototype_object_trim */
 
 /**
diff --git a/src/libecmabuiltins/ecma-builtins-internal.h b/src/libecmabuiltins/ecma-builtins-internal.h
index ed55509b7..03e046706 100644
--- a/src/libecmabuiltins/ecma-builtins-internal.h
+++ b/src/libecmabuiltins/ecma-builtins-internal.h
@@ -169,4 +169,19 @@ ECMA_BUILTIN_LIST (DECLARE_DISPATCH_ROUTINES)
 #undef DECLARE_PROPERTY_NUMBER_VARIABLES
 #undef DECLARE_DISPATCH_ROUTINES
 
+#ifndef CONFIG_ECMA_COMPACT_PROFILE
+# define ECMA_BUILTIN_CP_UNIMPLEMENTED(...) \
+  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS ("Compact Profile optional built-in.", __VA_ARGS__)
+#else /* !CONFIG_ECMA_COMPACT_PROFILE */
+# define ECMA_BUILTIN_CP_UNIMPLEMENTED(...) \
+{ \
+  if (false) \
+  { \
+    jerry_ref_unused_variables (0, __VA_ARGS__); \
+  } \
+  ecma_object_t *cp_error_p = ecma_builtin_get (ECMA_BUILTIN_ID_COMPACT_PROFILE_ERROR); \
+  return ecma_make_throw_obj_completion_value (cp_error_p); \
+}
+#endif /* CONFIG_ECMA_COMPACT_PROFILE */
+
 #endif /* !ECMA_BUILTINS_INTERNAL_H */
diff --git a/src/libecmabuiltins/ecma-builtins.c b/src/libecmabuiltins/ecma-builtins.c
index 693b89f33..5d27021d6 100644
--- a/src/libecmabuiltins/ecma-builtins.c
+++ b/src/libecmabuiltins/ecma-builtins.c
@@ -268,7 +268,11 @@ ecma_builtin_try_to_instantiate_property (ecma_object_t *object_p, /**< object *
 
     default:
     {
-      JERRY_UNIMPLEMENTED ();
+#ifdef CONFIG_ECMA_COMPACT_PROFILE
+      JERRY_UNREACHABLE ();
+#else /* CONFIG_ECMA_COMPACT_PROFILE */
+      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
     }
   }
 
@@ -408,7 +412,11 @@ ecma_builtin_dispatch_call (ecma_object_t *obj_p, /**< built-in object */
 
       default:
       {
-        JERRY_UNIMPLEMENTED ();
+#ifdef CONFIG_ECMA_COMPACT_PROFILE
+        JERRY_UNREACHABLE ();
+#else /* CONFIG_ECMA_COMPACT_PROFILE */
+        JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
       }
     }
   }
@@ -468,7 +476,11 @@ ecma_builtin_dispatch_construct (ecma_object_t *obj_p, /**< built-in object */
 
     default:
     {
-      JERRY_UNIMPLEMENTED ();
+#ifdef CONFIG_ECMA_COMPACT_PROFILE
+      JERRY_UNREACHABLE ();
+#else /* CONFIG_ECMA_COMPACT_PROFILE */
+      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
     }
   }
 
@@ -510,7 +522,11 @@ ecma_builtin_get_routine_parameters_number (ecma_builtin_id_t builtin_id, /**< i
 
     default:
     {
-      JERRY_UNIMPLEMENTED ();
+#ifdef CONFIG_ECMA_COMPACT_PROFILE
+      JERRY_UNREACHABLE ();
+#else /* CONFIG_ECMA_COMPACT_PROFILE */
+      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
     }
   }
 
@@ -557,7 +573,11 @@ ecma_builtin_dispatch_routine (ecma_builtin_id_t builtin_object_id, /**< built-i
 
     default:
     {
-      JERRY_UNIMPLEMENTED ();
+#ifdef CONFIG_ECMA_COMPACT_PROFILE
+      JERRY_UNREACHABLE ();
+#else /* CONFIG_ECMA_COMPACT_PROFILE */
+      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+#endif /* !CONFIG_ECMA_COMPACT_PROFILE */
     }
   }
 
diff --git a/src/libecmaobjects/ecma-gc.c b/src/libecmaobjects/ecma-gc.c
index ed6785d5f..3c7d284fe 100644
--- a/src/libecmaobjects/ecma-gc.c
+++ b/src/libecmaobjects/ecma-gc.c
@@ -393,7 +393,7 @@ ecma_gc_mark (ecma_object_t *object_p, /**< start object */
           case ECMA_INTERNAL_PROPERTY_NUMBER_INDEXED_ARRAY_VALUES: /* a collection of ecma-values */
           case ECMA_INTERNAL_PROPERTY_STRING_INDEXED_ARRAY_VALUES: /* a collection of ecma-values */
           {
-            JERRY_UNIMPLEMENTED();
+            JERRY_UNIMPLEMENTED("Indexed array storage is not implemented yet.");
           }
 
           case ECMA_INTERNAL_PROPERTY_PROTOTYPE: /* the property's value is located in ecma_object_t
diff --git a/src/libecmaobjects/ecma-helpers-string.c b/src/libecmaobjects/ecma-helpers-string.c
index d48f8627a..425f1163a 100644
--- a/src/libecmaobjects/ecma-helpers-string.c
+++ b/src/libecmaobjects/ecma-helpers-string.c
@@ -306,7 +306,8 @@ ecma_copy_or_ref_ecma_string (ecma_string_t *string_desc_p) /**< string descript
     }
     else
     {
-      JERRY_UNIMPLEMENTED ();
+      JERRY_UNIMPLEMENTED ("Unimplemented copy operation for strings, "
+                           "stored in heap chunks or number, or concatenated strings.");
     }
   }
 
diff --git a/src/libecmaoperations/ecma-exceptions.c b/src/libecmaoperations/ecma-exceptions.c
index d1bfb1ee0..54adae93f 100644
--- a/src/libecmaoperations/ecma-exceptions.c
+++ b/src/libecmaoperations/ecma-exceptions.c
@@ -39,7 +39,7 @@ ecma_new_standard_error (ecma_standard_error_t error_type) /**< native error typ
   /* SyntaxError should be treated as an early error */
   JERRY_ASSERT (error_type != ECMA_ERROR_SYNTAX);
 
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(error_type);
+  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS("Built-in error objects are not implemented.", error_type);
 } /* ecma_new_standard_error */
 
 /**
diff --git a/src/libecmaoperations/ecma-function-object.c b/src/libecmaoperations/ecma-function-object.c
index 39f258b16..26c43560e 100644
--- a/src/libecmaoperations/ecma-function-object.c
+++ b/src/libecmaoperations/ecma-function-object.c
@@ -449,7 +449,7 @@ ecma_op_function_has_instance (ecma_object_t *func_obj_p, /**< Function object *
   {
     JERRY_ASSERT (ecma_get_object_type (func_obj_p) == ECMA_OBJECT_TYPE_BOUND_FUNCTION);
 
-    JERRY_UNIMPLEMENTED ();
+    JERRY_UNIMPLEMENTED ("Bound functions are not implemented.");
   }
 } /* ecma_op_function_has_instance */
 
@@ -557,7 +557,7 @@ ecma_op_function_call (ecma_object_t *func_obj_p, /**< Function object */
   {
     JERRY_ASSERT(ecma_get_object_type (func_obj_p) == ECMA_OBJECT_TYPE_BOUND_FUNCTION);
 
-    JERRY_UNIMPLEMENTED();
+    JERRY_UNIMPLEMENTED ("Bound functions are not implemented.");
   }
 } /* ecma_op_function_call */
 
@@ -654,7 +654,7 @@ ecma_op_function_construct (ecma_object_t *func_obj_p, /**< Function object */
   {
     JERRY_ASSERT(ecma_get_object_type (func_obj_p) == ECMA_OBJECT_TYPE_BOUND_FUNCTION);
 
-    JERRY_UNIMPLEMENTED();
+    JERRY_UNIMPLEMENTED ("Bound functions are not implemented.");
   }
 } /* ecma_op_function_construct */
 /**
@@ -779,7 +779,7 @@ ecma_op_get_throw_type_error (void)
 {
   TODO(Create [[ThrowTypeError]] during engine initialization and return it from here);
 
-  JERRY_UNIMPLEMENTED();
+  JERRY_UNIMPLEMENTED("Type error thrower is not implemented.");
 } /* ecma_op_get_throw_type_error */
 
 /**
diff --git a/src/libecmaoperations/ecma-objects.c b/src/libecmaoperations/ecma-objects.c
index 3d4b21912..a02402ac2 100644
--- a/src/libecmaoperations/ecma-objects.c
+++ b/src/libecmaoperations/ecma-objects.c
@@ -68,7 +68,7 @@ ecma_op_object_get (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -126,7 +126,7 @@ ecma_op_object_get_own_property (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -176,7 +176,7 @@ ecma_op_object_get_property (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -219,7 +219,7 @@ ecma_op_object_put (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -260,7 +260,7 @@ ecma_op_object_can_put (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -301,7 +301,7 @@ ecma_op_object_has_property (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -347,7 +347,7 @@ ecma_op_object_delete (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -387,7 +387,7 @@ ecma_op_object_default_value (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -438,7 +438,7 @@ ecma_op_object_define_own_property (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
@@ -479,7 +479,7 @@ ecma_op_object_has_instance (ecma_object_t *obj_p, /**< the object */
 
     case ECMA_OBJECT_TYPE_HOST:
     {
-      JERRY_UNIMPLEMENTED();
+      JERRY_UNIMPLEMENTED("Host objects support is not implemented.");
     }
   }
 
diff --git a/src/libperipherals/common-io.c b/src/libperipherals/common-io.c
index f11f6910c..4f60fcac6 100644
--- a/src/libperipherals/common-io.c
+++ b/src/libperipherals/common-io.c
@@ -22,25 +22,25 @@
 int
 digital_read (uint32_t arg1 __unused, uint32_t arg2 __unused)
 {
-  JERRY_UNIMPLEMENTED ();
+  JERRY_UNIMPLEMENTED ("Digital read operation is not implemented.");
 }
 
 void
 digital_write (uint32_t arg1 __unused, uint32_t arg2 __unused)
 {
-  JERRY_UNIMPLEMENTED ();
+  JERRY_UNIMPLEMENTED ("Digital write operation is not implemented.");
 }
 
 int
 analog_read (uint32_t arg1 __unused, uint32_t arg2 __unused)
 {
-  JERRY_UNIMPLEMENTED ();
+  JERRY_UNIMPLEMENTED ("Analog read operation is not implemented.");
 }
 
 void
 analog_write (uint32_t arg1 __unused, uint32_t arg2 __unused)
 {
-  JERRY_UNIMPLEMENTED ();
+  JERRY_UNIMPLEMENTED ("Analog write operation is not implemented.");
 }
 
 #ifdef __TARGET_HOST
diff --git a/src/libruntime/jerry-libc-printf.c b/src/libruntime/jerry-libc-printf.c
index 668aa0a50..8fe0331d8 100644
--- a/src/libruntime/jerry-libc-printf.c
+++ b/src/libruntime/jerry-libc-printf.c
@@ -530,7 +530,8 @@ __vfprintf (_FILE *stream, /**< stream pointer */
 
       if (*format_iter_p == '*')
       {
-        JERRY_UNIMPLEMENTED();
+        /* Not supported */
+        JERRY_UNREACHABLE ();
       }
 
       // If there is a number, recognize it as field width
@@ -543,7 +544,8 @@ __vfprintf (_FILE *stream, /**< stream pointer */
 
       if (*format_iter_p == '.')
       {
-        JERRY_UNIMPLEMENTED();
+        /* Not supported */
+        JERRY_UNREACHABLE ();
       }
 
       switch (*format_iter_p)
@@ -636,7 +638,8 @@ __vfprintf (_FILE *stream, /**< stream pointer */
         case 'a':
         case 'A':
         {
-          JERRY_UNIMPLEMENTED();
+          /* Not supported */
+          JERRY_UNREACHABLE ();
           break;
         }
 
@@ -644,7 +647,8 @@ __vfprintf (_FILE *stream, /**< stream pointer */
         {
           if (length & LIBC_PRINTF_ARG_LENGTH_TYPE_L)
           {
-            JERRY_UNIMPLEMENTED();
+            /* Not supported */
+            JERRY_UNREACHABLE ();
           }
           else
           {
@@ -667,7 +671,8 @@ __vfprintf (_FILE *stream, /**< stream pointer */
         {
           if (length & LIBC_PRINTF_ARG_LENGTH_TYPE_L)
           {
-            JERRY_UNIMPLEMENTED();
+            /* Not supported */
+            JERRY_UNREACHABLE ();
           }
           else
           {
@@ -707,7 +712,8 @@ __vfprintf (_FILE *stream, /**< stream pointer */
 
         case 'n':
         {
-          JERRY_UNIMPLEMENTED();
+          /* Not supported */
+          JERRY_UNREACHABLE ();
           break;
         }
       }
diff --git a/src/libruntime/target/linux/jerry-libc.c b/src/libruntime/target/linux/jerry-libc.c
index a81c582a2..66cf5dab0 100644
--- a/src/libruntime/target/linux/jerry-libc.c
+++ b/src/libruntime/target/linux/jerry-libc.c
@@ -186,7 +186,8 @@ __fopen (const char *path, /**< file path */
       create_if_not_exist = true;
       if (mode[1] == '+')
       {
-        JERRY_UNIMPLEMENTED();
+        /* Not supported */
+        JERRY_UNREACHABLE();
       }
       break;
     }
diff --git a/src/libruntime/target/stm32f3/jerry-libc.c b/src/libruntime/target/stm32f3/jerry-libc.c
index cb8ca0391..916c2de30 100644
--- a/src/libruntime/target/stm32f3/jerry-libc.c
+++ b/src/libruntime/target/stm32f3/jerry-libc.c
@@ -27,7 +27,7 @@ extern void __noreturn exit (int status);
 int
 __putchar (int c)
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(c);
+  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS("putchar is not implemented for STM32F3.", c);
 } /* __putchar */
 
 /** exit - cause normal process termination  */
@@ -54,6 +54,6 @@ __fwrite (const void *ptr, /**< data to write */
          size_t nmemb, /**< number of elements */
          _FILE *stream) /**< stream pointer */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(ptr, size, nmemb, stream);
+  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS("fwrite is not implemented for STM32F3.", ptr, size, nmemb, stream);
 } /* __fwrite */
 
diff --git a/src/libruntime/target/stm32f4/jerry-libc.c b/src/libruntime/target/stm32f4/jerry-libc.c
index cb8ca0391..d0fdfc857 100644
--- a/src/libruntime/target/stm32f4/jerry-libc.c
+++ b/src/libruntime/target/stm32f4/jerry-libc.c
@@ -27,7 +27,7 @@ extern void __noreturn exit (int status);
 int
 __putchar (int c)
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(c);
+  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS("putchar is not implemented for STM32F4.", c);
 } /* __putchar */
 
 /** exit - cause normal process termination  */
@@ -54,6 +54,6 @@ __fwrite (const void *ptr, /**< data to write */
          size_t nmemb, /**< number of elements */
          _FILE *stream) /**< stream pointer */
 {
-  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(ptr, size, nmemb, stream);
+  JERRY_UNIMPLEMENTED_REF_UNUSED_VARS("fwrite is not implemented for STM32F4.", ptr, size, nmemb, stream);
 } /* __fwrite */