diff --git a/jerry-core/lit/lit-char-helpers.cpp b/jerry-core/lit/lit-char-helpers.cpp
index 0f83bc05a..0019fa117 100644
--- a/jerry-core/lit/lit-char-helpers.cpp
+++ b/jerry-core/lit/lit-char-helpers.cpp
@@ -15,6 +15,8 @@
 
 #include "lit-char-helpers.h"
 
+#include "lit-strings.h"
+
 /**
  * Check if specified character is one of the Format-Control characters
  *
@@ -112,6 +114,10 @@ lit_char_is_unicode_letter (ecma_char_t c) /**< code unit */
   {
     return true;
   }
+  else if (c <= LIT_UTF8_1_BYTE_CODE_POINT_MAX)
+  {
+    return false;
+  }
 
   /* Lu */
 #define LIT_UNICODE_RANGE_LU(range_begin, range_end) \