--- a/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/ScriptObject.java	Mon Mar 26 15:09:20 2018 +0200
+++ b/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/ScriptObject.java	Mon Mar 26 19:27:45 2018 +0530
@@ -2046,8 +2046,11 @@
     // Marks a property as declared and sets its value. Used as slow path for block-scoped LET and CONST
     @SuppressWarnings("unused")
     private void declareAndSet(final String key, final Object value) {
+        declareAndSet(findProperty(key, false), value);
+    }
+
+    private void declareAndSet(final FindProperty find, final Object value) {
         final PropertyMap oldMap = getMap();
-        final FindProperty find = findProperty(key, false);
         assert find != null;
 
         final Property property = find.getProperty();
@@ -2056,7 +2059,7 @@
 
         final PropertyMap newMap = oldMap.replaceProperty(property, property.removeFlags(Property.NEEDS_DECLARATION));
         setMap(newMap);
-        set(key, value, NashornCallSiteDescriptor.CALLSITE_DECLARE);
+        set(property.getKey(), value, NashornCallSiteDescriptor.CALLSITE_DECLARE);
     }
 
     /**
@@ -3089,6 +3092,11 @@
                 return;
             }
 
+            if (NashornCallSiteDescriptor.isDeclaration(callSiteFlags) && f.getProperty().needsDeclaration()) {
+                f.getOwner().declareAndSet(f, value);
+                return;
+            }
+
             f.setValue(value, isStrictFlag(callSiteFlags));
 
         } else if (!isExtensible()) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/nashorn/script/trusted/JDK-8200215.js	Mon Mar 26 19:27:45 2018 +0530
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2018, 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-8200215: 17th loop of "let foo = ''"; throws ReferenceError
+ *
+ * @test
+ * @run
+ */
+
+var NashornScriptEngineFactory = Java.type("jdk.nashorn.api.scripting.NashornScriptEngineFactory");
+var factory = new NashornScriptEngineFactory();
+var engine = factory.getScriptEngine("-strict", "--language=es6");
+var bindings = engine.createBindings();
+for (var i = 0; i < 17; i++) {
+    bindings.eval("let foo = '';\n");
+}