diff --git a/js/tests/js1_7/block/regress-344139.js b/js/tests/js1_7/block/regress-344139.js
new file mode 100755
index 000000000000..a9ba191e6687
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+++ b/js/tests/js1_7/block/regress-344139.js
@@ -0,0 +1,123 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (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.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is JavaScript Engine testing utilities.
+ *
+ * The Initial Developer of the Original Code is
+ * Jeff Walden <jwalden+code@mit.edu>.
+ * Portions created by the Initial Developer are Copyright (C) 2006
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+//-----------------------------------------------------------------------------
+var bug     = "344139";
+var summary = "Basic let functionality";
+var actual, expect;
+
+printBugNumber(bug);
+printStatus(summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+var failed = false;
+
+var x = 7;
+
+function f1()
+{
+  let x = 5;
+  return x;
+}
+
+function f2()
+{
+  let x = 5;
+  x = 3;
+  return x;
+}
+
+function f3()
+{
+  let x = 5;
+  x += x;
+  return x;
+}
+
+function f4()
+{
+  var v = 5;
+  let q = 17;
+
+  // 0+1+2+...+8+9 == 45
+  for (let v = 0; v < 10; v++)
+    q += v;
+
+  if (q != 62)
+    throw "f4(): wrong value for q\n" +
+          "  expected: 62\n" +
+          "  actual:   " + q;
+
+  return v;
+}
+
+try
+{
+  if (f1() != 5 || x != 7)
+    throw "f1() == 5";
+  if (f2() != 3 || x != 7)
+    throw "f2() == 3";
+  if (f3() != 10 || x != 7)
+    throw "f3() == 10";
+
+  if (f4() != 5)
+    throw "f4() == 5";
+
+  var bad = true;
+  try
+  {
+    eval("q++"); // force error at runtime
+  }
+  catch (e)
+  {
+    if (e instanceof ReferenceError)
+      bad = false;
+  }
+  if (bad)
+    throw "f4(): q escaping scope!";
+}
+catch (e)
+{
+  failed = e;
+}
+
+expect = false;
+actual = failed;
+
+reportCompare(expect, actual, summary);