--- a/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/codegen/CodeGenerator.java	Tue Mar 22 14:23:16 2016 +0100
+++ b/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/codegen/CodeGenerator.java	Tue Mar 22 14:26:20 2016 +0100
@@ -3312,8 +3312,10 @@
         final boolean needsScope = identSymbol.isScope();
 
         if (init == null) {
-            if (needsScope && varNode.isBlockScoped()) {
-                // block scoped variables need a DECLARE flag to signal end of temporal dead zone (TDZ)
+            // Block-scoped variables need a DECLARE flag to signal end of temporal dead zone (TDZ).
+            // However, don't do this for CONST which always has an initializer except in the special case of
+            // for-in/of loops, in which it is initialized in the loop header and should be left untouched here.
+            if (needsScope && varNode.isLet()) {
                 method.loadCompilerConstant(SCOPE);
                 method.loadUndefined(Type.OBJECT);
                 final int flags = getScopeCallSiteFlags(identSymbol) | (varNode.isBlockScoped() ? CALLSITE_DECLARE : 0);

--- a/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/parser/Parser.java	Tue Mar 22 14:23:16 2016 +0100
+++ b/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/parser/Parser.java	Tue Mar 22 14:26:20 2016 +0100
@@ -1258,9 +1258,7 @@
                 break;
             default:
                 if (useBlockScope() && (type == LET || type == CONST)) {
-                    if (type == LET) {
-                        flags |= ForNode.PER_ITERATION_SCOPE;
-                    }
+                    flags |= ForNode.PER_ITERATION_SCOPE;
                     // LET/CONST declaration captured in container block created above.
                     vars = variableStatement(type, false, forStart);
                     break;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nashorn/test/script/basic/es6/JDK-8151811.js	Tue Mar 22 14:26:20 2016 +0100
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ * 
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ * 
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ * 
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ * 
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * JDK-8151811: Const declarations do not work in for..in loops
+ *
+ * @test
+ * @run
+ * @option --language=es6
+ */
+
+let array = ["a", "b", "c"];
+let count = 0;
+
+for (const i in array) {
+    try {
+        eval("i = 5");
+        fail("const assignment should have thrown")
+    } catch (e) {
+        Assert.assertTrue(e instanceof TypeError);
+    }
+    Assert.assertTrue(i == count++);
+}
+
+let funcs = [];
+
+for (const i in array) {
+    try {
+        eval("i = 5");
+        fail("const assignment should have thrown")
+    } catch (e) {
+        Assert.assertTrue(e instanceof TypeError);
+    }
+    for (const j in array) {
+        for (const k in array) {
+            funcs.push(function () {
+                return array[i] + array[j] + array[k];
+            });
+        }
+    }
+}
+
+Assert.assertEquals(funcs.length, 3 * 3 * 3);
+count = 0;
+
+for (let i = 0; i < 3; i++) {
+    for (let j = 0; j < 3; j++) {
+        for (let k = 0; k < 3; k++) {
+            Assert.assertEquals(funcs[count++](), array[i] + array[j] + array[k]);
+        }
+    }
+}