diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-json.c b/jerry-core/ecma/builtin-objects/ecma-builtin-json.c
index 0e0112798a..dc57f195d1 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-json.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-json.c
@@ -183,7 +183,7 @@ ecma_builtin_json_parse_string (ecma_json_token_t *token_p) /**< token argument
         case LIT_CHAR_LOWERCASE_U:
         {
           ecma_char_t code_unit;
-          if ((end_p - current_p >= 2) && !(lit_read_code_unit_from_hex (current_p + 1, 4, &code_unit)))
+          if ((end_p - current_p < 4) || !(lit_read_code_unit_from_hex (current_p + 1, 4, &code_unit)))
           {
             return;
           }