diff --git a/jerry-core/parser/js/lexer.cpp b/jerry-core/parser/js/lexer.cpp
index b7cdbc1c7..b185139b6 100644
--- a/jerry-core/parser/js/lexer.cpp
+++ b/jerry-core/parser/js/lexer.cpp
@@ -1761,6 +1761,42 @@ lexer_are_tokens_with_same_identifier (token id1, /**< identifier token (TOK_NAM
   return (id1.uid == id2.uid);
 } /* lexer_are_tokens_with_same_identifier */
 
+/**
+ * Checks that TOK_STRING doesn't contain EscapeSequence or LineContinuation
+ *
+ * @return true, if token's string in source buffer doesn't contain backslash
+ *         false, otherwise
+ */
+bool
+lexer_is_no_escape_sequences_in_token_string (token tok) /**< token of type TOK_STRING */
+{
+  JERRY_ASSERT (tok.type == TOK_STRING);
+
+  lit_utf8_iterator_t iter = src_iter;
+  lit_utf8_iterator_seek (&iter, tok.loc);
+
+  JERRY_ASSERT (!lit_utf8_iterator_is_eos (&iter));
+  ecma_char_t c = lit_utf8_iterator_read_next (&iter);
+  JERRY_ASSERT (c == LIT_CHAR_SINGLE_QUOTE
+                || c == LIT_CHAR_DOUBLE_QUOTE);
+
+  const ecma_char_t end_char = c;
+
+  do
+  {
+    JERRY_ASSERT (!lit_utf8_iterator_is_eos (&iter));
+    c = lit_utf8_iterator_read_next (&iter);
+
+    if (c == LIT_CHAR_BACKSLASH)
+    {
+      return false;
+    }
+  }
+  while (c != end_char);
+
+  return true;
+} /* lexer_is_no_escape_sequences_in_token_string */
+
 /**
  * Initialize lexer to start parsing of a new source
  */
diff --git a/jerry-core/parser/js/lexer.h b/jerry-core/parser/js/lexer.h
index 8de1a90d3..34c434174 100644
--- a/jerry-core/parser/js/lexer.h
+++ b/jerry-core/parser/js/lexer.h
@@ -187,4 +187,6 @@ void lexer_set_strict_mode (bool);
 
 extern bool lexer_are_tokens_with_same_identifier (token id1, token id2);
 
+extern bool lexer_is_no_escape_sequences_in_token_string (token);
+
 #endif
diff --git a/jerry-core/parser/js/parser.cpp b/jerry-core/parser/js/parser.cpp
index 68fe1f5ea..7664dd702 100644
--- a/jerry-core/parser/js/parser.cpp
+++ b/jerry-core/parser/js/parser.cpp
@@ -2886,7 +2886,8 @@ preparse_scope (bool is_global)
    */
   while (token_is (TOK_STRING))
   {
-    if (lit_literal_equal_type_cstr (lit_get_literal_by_cp (token_data_as_lit_cp ()), "use strict"))
+    if (lit_literal_equal_type_cstr (lit_get_literal_by_cp (token_data_as_lit_cp ()), "use strict")
+        && lexer_is_no_escape_sequences_in_token_string (tok))
     {
       scopes_tree_set_strict_mode (STACK_TOP (scopes), true);
       is_use_strict = true;