diff --git a/jerry-core/parser/js/js-lexer.c b/jerry-core/parser/js/js-lexer.c
index f7bd5b952..699dd8c42 100644
--- a/jerry-core/parser/js/js-lexer.c
+++ b/jerry-core/parser/js/js-lexer.c
@@ -1821,7 +1821,19 @@ lexer_construct_regexp_object (parser_context_t *context_p, /**< context */
   const re_compiled_code_t *re_bytecode_p = NULL;
   ecma_value_t completion_value;
 
-  ecma_string_t *pattern_str_p = ecma_new_ecma_string_from_utf8 (regex_start_p, length);
+  ecma_string_t *pattern_str_p = NULL;
+
+  if (lit_is_valid_cesu8_string (regex_start_p, length))
+  {
+    pattern_str_p = ecma_new_ecma_string_from_utf8 (regex_start_p, length);
+  }
+  else
+  {
+    JERRY_ASSERT (lit_is_valid_utf8_string (regex_start_p, length));
+    pattern_str_p = ecma_new_ecma_string_from_utf8_converted_to_cesu8 (regex_start_p, length);
+  }
+
+
   completion_value = re_compile_bytecode (&re_bytecode_p,
                                           pattern_str_p,
                                           current_flags);
diff --git a/tests/jerry/fail/regression-test-issue-1831.js b/tests/jerry/fail/regression-test-issue-1831.js
new file mode 100644
index 000000000..26b5ebf75
--- /dev/null
+++ b/tests/jerry/fail/regression-test-issue-1831.js
@@ -0,0 +1,15 @@
+// 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.
+
+/኱𞻲/‌ஃ︠﹍