diff --git a/jerry-core/ecma/base/ecma-gc.cpp b/jerry-core/ecma/base/ecma-gc.cpp
index 21c1ab083..6e22dce57 100644
--- a/jerry-core/ecma/base/ecma-gc.cpp
+++ b/jerry-core/ecma/base/ecma-gc.cpp
@@ -580,14 +580,9 @@ ecma_try_to_give_back_some_memory (mem_try_give_memory_back_severity_t severity)
       ecma_gc_run ();
     }
   }
-  else if (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_MEDIUM
-           || severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH)
-  {
-    ecma_gc_run ();
-  }
   else
   {
-    JERRY_ASSERT (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL);
+    JERRY_ASSERT (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH);
 
     /* Freeing as much memory as we currently can */
     ecma_lcache_invalidate_all ();
diff --git a/jerry-core/mem/mem-allocator.h b/jerry-core/mem/mem-allocator.h
index cb70304e0..306c9a210 100644
--- a/jerry-core/mem/mem-allocator.h
+++ b/jerry-core/mem/mem-allocator.h
@@ -62,17 +62,15 @@ typedef uint16_t mem_cpointer_t;
  * Severity of a 'try give memory back' request
  *
  * The request are posted sequentially beginning from
- * low to critical until enough memory is freed.
+ * low to high until enough memory is freed.
  *
- * If not enough memory is freed upon a critical request
+ * If not enough memory is freed upon a high request
  * then the engine is shut down with ERR_OUT_OF_MEMORY.
  */
 typedef enum
 {
   MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_LOW, /* 'low' severity */
-  MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_MEDIUM, /* 'medium' severity */
   MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH, /* 'high' severity */
-  MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL /* 'critical' severity */
 } mem_try_give_memory_back_severity_t;
 
 /**
diff --git a/jerry-core/mem/mem-heap.cpp b/jerry-core/mem/mem-heap.cpp
index d778db331..521c9c17a 100644
--- a/jerry-core/mem/mem-heap.cpp
+++ b/jerry-core/mem/mem-heap.cpp
@@ -531,7 +531,7 @@ mem_heap_alloc_block_try_give_memory_back (size_t size_in_bytes, /**< size of re
   VALGRIND_FREYA_CHECK_MEMPOOL_REQUEST;
 
 #ifdef MEM_GC_BEFORE_EACH_ALLOC
-  mem_run_try_to_give_memory_back_callbacks (MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL);
+  mem_run_try_to_give_memory_back_callbacks (MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH);
 #endif /* MEM_GC_BEFORE_EACH_ALLOC */
 
   size_t chunks = mem_get_block_chunks_count_from_data_size (size_in_bytes);
@@ -549,14 +549,14 @@ mem_heap_alloc_block_try_give_memory_back (size_t size_in_bytes, /**< size of re
   }
 
   for (mem_try_give_memory_back_severity_t severity = MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_LOW;
-       severity <= MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL;
+       severity <= MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH;
        severity = (mem_try_give_memory_back_severity_t) (severity + 1))
   {
     mem_run_try_to_give_memory_back_callbacks (severity);
 
     data_space_p = mem_heap_alloc_block_internal (size_in_bytes, length_type, alloc_term);
 
-    if (data_space_p != NULL)
+    if (likely (data_space_p != NULL))
     {
       VALGRIND_FREYA_MALLOCLIKE_SPACE (data_space_p, size_in_bytes);
       return data_space_p;
diff --git a/jerry-core/mem/mem-poolman.cpp b/jerry-core/mem/mem-poolman.cpp
index 239cbfa87..8ee38f5e6 100644
--- a/jerry-core/mem/mem-poolman.cpp
+++ b/jerry-core/mem/mem-poolman.cpp
@@ -536,7 +536,7 @@ uint8_t* __attr_always_inline___
 mem_pools_alloc (void)
 {
 #ifdef MEM_GC_BEFORE_EACH_ALLOC
-  mem_run_try_to_give_memory_back_callbacks (MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL);
+  mem_run_try_to_give_memory_back_callbacks (MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH);
 #endif /* MEM_GC_BEFORE_EACH_ALLOC */
 
   mem_check_pools ();
diff --git a/jerry-core/vm/vm.cpp b/jerry-core/vm/vm.cpp
index b981a1319..f5088993d 100644
--- a/jerry-core/vm/vm.cpp
+++ b/jerry-core/vm/vm.cpp
@@ -103,7 +103,7 @@ interp_mem_get_stats (mem_heap_stats_t *out_heap_stats_p,
   }
 
   /* Requesting to free as much memory as we currently can */
-  ecma_try_to_give_back_some_memory (MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL);
+  ecma_try_to_give_back_some_memory (MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH);
 
   if (reset_peak_before)
   {
diff --git a/tests/unit/test-heap.cpp b/tests/unit/test-heap.cpp
index ae1f4b684..26671f4df 100644
--- a/tests/unit/test-heap.cpp
+++ b/tests/unit/test-heap.cpp
@@ -42,17 +42,9 @@ test_heap_give_some_memory_back (mem_try_give_memory_back_severity_t severity)
   {
     p = 8;
   }
-  else if (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_MEDIUM)
-  {
-    p = 4;
-  }
-  else if (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH)
-  {
-    p = 2;
-  }
   else
   {
-    JERRY_ASSERT (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_CRITICAL);
+    JERRY_ASSERT (severity == MEM_TRY_GIVE_MEMORY_BACK_SEVERITY_HIGH);
 
     p = 1;
   }