diff --git a/jerry-core/parser/js/js-lexer.c b/jerry-core/parser/js/js-lexer.c
index e3b09ac69..c6132acb1 100644
--- a/jerry-core/parser/js/js-lexer.c
+++ b/jerry-core/parser/js/js-lexer.c
@@ -348,6 +348,16 @@ typedef struct
 #define LEXER_KEYWORD_LIST_LENGTH(name) (const uint8_t) (sizeof ((name)) / sizeof ((name)[0]))
 /** @} */
 
+/**
+ * Length of the shortest keyword.
+ */
+#define LEXER_KEYWORD_MIN_LENGTH 2
+
+/**
+ * Length of the longest keyword.
+ */
+#define LEXER_KEYWORD_MAX_LENGTH 10
+
 /**
  * Keywords with 2 characters.
  */
@@ -475,6 +485,10 @@ static const keyword_string_t * const keyword_strings_list[] =
   keywords_with_length_10
 };
 
+JERRY_STATIC_ASSERT (sizeof (keyword_strings_list) / sizeof (const keyword_string_t *)
+                     == (LEXER_KEYWORD_MAX_LENGTH - LEXER_KEYWORD_MIN_LENGTH) + 1,
+                     keyword_strings_list_size_must_equal_to_keyword_max_length_difference);
+
 /**
  * List of the keyword groups length.
  */
@@ -510,7 +524,7 @@ lexer_parse_identifier (parser_context_t *context_p, /**< context */
   size_t length = 0;
 
   context_p->token.type = LEXER_LITERAL;
-  context_p->token.literal_is_reserved = false;
+  context_p->token.ident_is_strict_keyword = false;
   context_p->token.lit_location.type = LEXER_IDENT_LITERAL;
   context_p->token.lit_location.has_escape = false;
 
@@ -574,21 +588,30 @@ lexer_parse_identifier (parser_context_t *context_p, /**< context */
 
   context_p->source_p = ident_start_p;
   context_p->token.column = context_p->column;
+  context_p->token.lit_location.char_p = ident_start_p;
+  context_p->token.lit_location.length = (prop_length_t) length;
 
   if (length > PARSER_MAXIMUM_IDENT_LENGTH)
   {
     parser_raise_error (context_p, PARSER_ERR_IDENTIFIER_TOO_LONG);
   }
 
-  /* Check keywords (Only if there is no \u escape sequence in the pattern). */
+  /* Check keywords. */
   if (check_keywords
-      && !context_p->token.lit_location.has_escape
-      && (length >= 2 && length <= 10))
+      && (length >= LEXER_KEYWORD_MIN_LENGTH && length <= LEXER_KEYWORD_MAX_LENGTH))
   {
-    const keyword_string_t *keyword_list_p = keyword_strings_list[length - 2];
+    uint8_t buffer_p[LEXER_KEYWORD_MAX_LENGTH];
+
+    if (JERRY_UNLIKELY (context_p->token.lit_location.has_escape))
+    {
+      lexer_convert_ident_to_cesu8 (ident_start_p, buffer_p, (prop_length_t) length);
+      ident_start_p = buffer_p;
+    }
+
+    const keyword_string_t *keyword_list_p = keyword_strings_list[length - LEXER_KEYWORD_MIN_LENGTH];
 
     int start = 0;
-    int end = keyword_lengths_list[length - 2];
+    int end = keyword_lengths_list[length - LEXER_KEYWORD_MIN_LENGTH];
     int middle = end / 2;
 
     do
@@ -607,6 +630,11 @@ lexer_parse_identifier (parser_context_t *context_p, /**< context */
 #if ENABLED (JERRY_ES2015)
             if (keyword_p->type == LEXER_KEYW_YIELD && (context_p->status_flags & PARSER_IS_GENERATOR_FUNCTION))
             {
+              if (ident_start_p == buffer_p)
+              {
+                parser_raise_error (context_p, PARSER_ERR_INVALID_KEYWORD);
+              }
+
               if (context_p->status_flags & PARSER_DISALLOW_YIELD)
               {
                 parser_raise_error (context_p, PARSER_ERR_YIELD_NOT_ALLOWED);
@@ -622,10 +650,15 @@ lexer_parse_identifier (parser_context_t *context_p, /**< context */
               parser_raise_error (context_p, PARSER_ERR_STRICT_IDENT_NOT_ALLOWED);
             }
 
-            context_p->token.literal_is_reserved = true;
+            context_p->token.ident_is_strict_keyword = true;
             break;
           }
 
+          if (ident_start_p == buffer_p)
+          {
+            parser_raise_error (context_p, PARSER_ERR_INVALID_KEYWORD);
+          }
+
           context_p->token.type = (uint8_t) keyword_p->type;
           break;
         }
@@ -646,13 +679,6 @@ lexer_parse_identifier (parser_context_t *context_p, /**< context */
     while (start < end);
   }
 
-  if (context_p->token.type == LEXER_LITERAL)
-  {
-    /* Fill literal data. */
-    context_p->token.lit_location.char_p = ident_start_p;
-    context_p->token.lit_location.length = (prop_length_t) length;
-  }
-
   context_p->source_p = source_p;
   context_p->column = column;
 } /* lexer_parse_identifier */
@@ -964,7 +990,7 @@ lexer_parse_number (parser_context_t *context_p) /**< context */
   size_t length;
 
   context_p->token.type = LEXER_LITERAL;
-  context_p->token.literal_is_reserved = false;
+  context_p->token.ident_is_strict_keyword = false;
   context_p->token.extra_value = LEXER_NUMBER_DECIMAL;
   context_p->token.lit_location.char_p = source_p;
   context_p->token.lit_location.type = LEXER_NUMBER_LITERAL;
@@ -1688,9 +1714,9 @@ lexer_process_char_literal (parser_context_t *context_p, /**< context */
  * Convert an ident with escapes to a utf8 string.
  */
 void
-lexer_convert_ident_to_utf8 (const uint8_t *source_p, /**< source string */
-                             uint8_t *destination_p, /**< destination string */
-                             prop_length_t length) /**< length of destination string */
+lexer_convert_ident_to_cesu8 (const uint8_t *source_p, /**< source string */
+                              uint8_t *destination_p, /**< destination string */
+                              prop_length_t length) /**< length of destination string */
 {
   const uint8_t *destination_end_p = destination_p + length;
 
@@ -1712,7 +1738,7 @@ lexer_convert_ident_to_utf8 (const uint8_t *source_p, /**< source string */
     *destination_p++ = *source_p++;
   }
   while (destination_p < destination_end_p);
-} /* lexer_convert_ident_to_utf8 */
+} /* lexer_convert_ident_to_cesu8 */
 
 /**
  * Construct a literal object from an identifier.
@@ -1748,7 +1774,7 @@ lexer_construct_literal_object (parser_context_t *context_p, /**< context */
 
     if (literal_p->type == LEXER_IDENT_LITERAL)
     {
-      lexer_convert_ident_to_utf8 (source_p, destination_start_p, literal_p->length);
+      lexer_convert_ident_to_cesu8 (source_p, destination_start_p, literal_p->length);
     }
     else
     {
@@ -2412,7 +2438,7 @@ lexer_construct_regexp_object (parser_context_t *context_p, /**< context */
   literal_p->u.bytecode_p = (ecma_compiled_code_t *) re_bytecode_p;
 
   context_p->token.type = LEXER_LITERAL;
-  context_p->token.literal_is_reserved = false;
+  context_p->token.ident_is_strict_keyword = false;
   context_p->token.lit_location.type = LEXER_REGEXP_LITERAL;
 
   context_p->lit_object.literal_p = literal_p;
@@ -2479,7 +2505,7 @@ lexer_expect_identifier (parser_context_t *context_p, /**< context */
     /* When parsing default exports for modules, it is not required by functions or classes to have identifiers.
      * In this case we use a synthetic name for them. */
     context_p->token.type = LEXER_LITERAL;
-    context_p->token.literal_is_reserved = false;
+    context_p->token.ident_is_strict_keyword = false;
     context_p->token.lit_location.type = LEXER_IDENT_LITERAL;
     context_p->token.lit_location.has_escape = false;
     lexer_construct_literal_object (context_p, &lexer_default_literal, literal_type);
diff --git a/jerry-core/parser/js/js-lexer.h b/jerry-core/parser/js/js-lexer.h
index 64ca8f3be..fec1b2f08 100644
--- a/jerry-core/parser/js/js-lexer.h
+++ b/jerry-core/parser/js/js-lexer.h
@@ -288,8 +288,7 @@ typedef struct
 typedef struct
 {
   uint8_t type;                              /**< token type */
-  uint8_t literal_is_reserved;               /**< future reserved keyword
-                                              *   (when char_literal.type is LEXER_IDENT_LITERAL) */
+  uint8_t ident_is_strict_keyword;           /**< identifier is strict reserved keyword */
   uint8_t extra_value;                       /**< helper value for different purposes */
   uint8_t flags;                             /**< flag bits for the current token */
   parser_line_counter_t line;                /**< token start line */
diff --git a/jerry-core/parser/js/js-parser-expr.c b/jerry-core/parser/js/js-parser-expr.c
index b594f2ece..8d484286a 100644
--- a/jerry-core/parser/js/js-parser-expr.c
+++ b/jerry-core/parser/js/js-parser-expr.c
@@ -1054,7 +1054,7 @@ parser_parse_function_expression (parser_context_t *context_p, /**< context */
       }
 #endif /* ENABLED (JERRY_DEBUGGER) */
 
-      if (context_p->token.literal_is_reserved
+      if (context_p->token.ident_is_strict_keyword
           || context_p->lit_object.type != LEXER_LITERAL_OBJECT_ANY)
       {
         status_flags |= PARSER_HAS_NON_STRICT_ARG;
diff --git a/jerry-core/parser/js/js-parser-internal.h b/jerry-core/parser/js/js-parser-internal.h
index 43c532464..99254f91d 100644
--- a/jerry-core/parser/js/js-parser-internal.h
+++ b/jerry-core/parser/js/js-parser-internal.h
@@ -637,7 +637,7 @@ void lexer_parse_string (parser_context_t *context_p);
 void lexer_expect_identifier (parser_context_t *context_p, uint8_t literal_type);
 void lexer_scan_identifier (parser_context_t *context_p, uint32_t ident_opts);
 ecma_char_t lexer_hex_to_character (parser_context_t *context_p, const uint8_t *source_p, int length);
-void lexer_convert_ident_to_utf8 (const uint8_t *source_p, uint8_t *destination_p, prop_length_t length);
+void lexer_convert_ident_to_cesu8 (const uint8_t *source_p, uint8_t *destination_p, prop_length_t length);
 void lexer_expect_object_literal_id (parser_context_t *context_p, uint32_t ident_opts);
 void lexer_construct_literal_object (parser_context_t *context_p, const lexer_lit_location_t *literal_p,
                                      uint8_t literal_type);
diff --git a/jerry-core/parser/js/js-parser-module.c b/jerry-core/parser/js/js-parser-module.c
index dbefff399..e8336ce9c 100644
--- a/jerry-core/parser/js/js-parser-module.c
+++ b/jerry-core/parser/js/js-parser-module.c
@@ -367,7 +367,7 @@ parser_module_parse_export_clause (parser_context_t *context_p) /**< parser cont
     /* 15.2.3.1 The referenced binding cannot be a reserved word. */
     if (context_p->token.type != LEXER_LITERAL
         || context_p->token.lit_location.type != LEXER_IDENT_LITERAL
-        || context_p->token.literal_is_reserved)
+        || context_p->token.ident_is_strict_keyword)
     {
       parser_raise_error (context_p, PARSER_ERR_IDENTIFIER_EXPECTED);
     }
diff --git a/jerry-core/parser/js/js-parser-util.c b/jerry-core/parser/js/js-parser-util.c
index a1d6217fb..ee7361a6a 100644
--- a/jerry-core/parser/js/js-parser-util.c
+++ b/jerry-core/parser/js/js-parser-util.c
@@ -852,6 +852,10 @@ parser_error_to_string (parser_error_t error) /**< error code */
     {
       return "Character cannot be part of an identifier.";
     }
+    case PARSER_ERR_INVALID_KEYWORD:
+    {
+      return "Escape sequences are not allowed in keywords.";
+    }
     case PARSER_ERR_INVALID_NUMBER:
     {
       return "Invalid number.";
diff --git a/jerry-core/parser/js/js-parser.c b/jerry-core/parser/js/js-parser.c
index b08976868..37a6f3730 100644
--- a/jerry-core/parser/js/js-parser.c
+++ b/jerry-core/parser/js/js-parser.c
@@ -1729,7 +1729,7 @@ parser_parse_function_arguments (parser_context_t *context_p, /**< context */
                                     &context_p->token.lit_location,
                                     LEXER_IDENT_LITERAL);
 
-    if (context_p->token.literal_is_reserved
+    if (context_p->token.ident_is_strict_keyword
         || context_p->lit_object.type != LEXER_LITERAL_OBJECT_ANY)
     {
       context_p->status_flags |= PARSER_HAS_NON_STRICT_ARG;
diff --git a/jerry-core/parser/js/js-parser.h b/jerry-core/parser/js/js-parser.h
index 74d40d941..95f812bc0 100644
--- a/jerry-core/parser/js/js-parser.h
+++ b/jerry-core/parser/js/js-parser.h
@@ -48,6 +48,7 @@ typedef enum
   PARSER_ERR_INVALID_UNICODE_ESCAPE_SEQUENCE,         /**< invalid unicode escape sequence */
   PARSER_ERR_INVALID_IDENTIFIER_START,                /**< character cannot be start of an identifier */
   PARSER_ERR_INVALID_IDENTIFIER_PART,                 /**< character cannot be part of an identifier */
+  PARSER_ERR_INVALID_KEYWORD,                         /**< escape sequences are not allowed in keywords */
 
   PARSER_ERR_INVALID_NUMBER,                          /**< invalid number literal */
   PARSER_ERR_MISSING_EXPONENT,                        /**< missing exponent */
diff --git a/jerry-core/parser/js/js-scanner-util.c b/jerry-core/parser/js/js-scanner-util.c
index 6b09dcaae..cf0c19d01 100644
--- a/jerry-core/parser/js/js-scanner-util.c
+++ b/jerry-core/parser/js/js-scanner-util.c
@@ -1147,7 +1147,7 @@ scanner_scope_find_let_declaration (parser_context_t *context_p, /**< context */
   {
     uint8_t *destination_p = (uint8_t *) scanner_malloc (context_p, literal_p->length);
 
-    lexer_convert_ident_to_utf8 (literal_p->char_p, destination_p, literal_p->length);
+    lexer_convert_ident_to_cesu8 (literal_p->char_p, destination_p, literal_p->length);
 
     name_p = ecma_new_ecma_string_from_utf8 (destination_p, literal_p->length);
     scanner_free (destination_p, literal_p->length);
diff --git a/tests/jerry/keyword.js b/tests/jerry/keyword.js
new file mode 100644
index 000000000..558d2533a
--- /dev/null
+++ b/tests/jerry/keyword.js
@@ -0,0 +1,47 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+function check_syntax_error(code)
+{
+  try {
+    eval(code)
+    assert(false)
+  } catch (e) {
+    assert(e instanceof SyntaxError)
+  }
+}
+
+function check_strict_syntax_error(code)
+{
+  "use strict"
+
+  try {
+    eval(code)
+    assert(false)
+  } catch (e) {
+    assert(e instanceof SyntaxError)
+  }
+}
+
+check_syntax_error("d\\u006f {} while (false)")
+check_syntax_error("\\u0076\\u0061\\u0072 var = 5")
+check_syntax_error("wit\\u0068 ({}) {}")
+check_syntax_error("\\u0066alse")
+check_syntax_error("type\\006ff 3.14")
+check_syntax_error("try {} fin\\u0061lly {}")
+check_syntax_error("f\\u0075nction f() {}")
+check_syntax_error("a instanc\\u0065of b")
+
+check_strict_syntax_error("\\u006c\\u0065\\u0074 _let = 5");
+check_strict_syntax_error("\\u0070rotecte\\u0064");