diff --git a/jerry-core/parser/js/js-parser.c b/jerry-core/parser/js/js-parser.c
index 1b156a6de..922afabb2 100644
--- a/jerry-core/parser/js/js-parser.c
+++ b/jerry-core/parser/js/js-parser.c
@@ -290,7 +290,7 @@ parser_compute_indicies (parser_context_t *context_p, /**< context */
     {
       if (!(literal_p->status_flags & LEXER_FLAG_NO_REG_STORE))
       {
-        JERRY_ASSERT (register_count < PARSER_MAXIMUM_NUMBER_OF_REGISTERS);
+        JERRY_ASSERT (register_count <= PARSER_MAXIMUM_NUMBER_OF_REGISTERS);
         /* This var literal can be stored in a register. */
         literal_p->prop.index = register_index;
         register_index++;
diff --git a/tests/jerry/regression-test-issue-1556.js b/tests/jerry/regression-test-issue-1556.js
new file mode 100644
index 000000000..e1a59d36f
--- /dev/null
+++ b/tests/jerry/regression-test-issue-1556.js
@@ -0,0 +1,43 @@
+// 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.
+
+/* Maximum 256 paramaters are allowed. */
+var src = "(function (";
+for (var i = 0; i < 254; i++)
+    src += "a" + i + ", ";
+src += "b) { var c = 1; })()";
+
+eval(src);
+
+/* More than 256 parameters is a syntax error. */
+var src = "(function (";
+for (var i = 0; i < 255; i++)
+    src += "a" + i + ", ";
+src += "b) { })()";
+
+try {
+  eval(src);
+  assert(false);
+} catch (e) {
+  assert(e instanceof SyntaxError);
+}
+
+/* Maximum 256 local variables are stored in registers.
+ * The rest is stored in the lexical environment. */
+var src = "(function () {";
+for (var i = 0; i < 400; i++)
+    src += "var a" + i + " = 5; ";
+src += "})()";
+
+eval(src);