--- a/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/ScriptObject.java	Mon Apr 23 08:36:41 2018 -0700
+++ b/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/ScriptObject.java	Mon Apr 23 17:45:05 2018 +0200
@@ -2969,7 +2969,7 @@
     }
 
     private boolean doesNotHaveCheckArrayKeys(final long longIndex, final int value, final int callSiteFlags) {
-        if (getMap().containsArrayKeys()) {
+        if (hasDefinedArrayProperties()) {
             final String       key  = JSType.toString(longIndex);
             final FindProperty find = findProperty(key, true);
             if (find != null) {
@@ -2981,7 +2981,7 @@
     }
 
     private boolean doesNotHaveCheckArrayKeys(final long longIndex, final double value, final int callSiteFlags) {
-         if (getMap().containsArrayKeys()) {
+         if (hasDefinedArrayProperties()) {
             final String       key  = JSType.toString(longIndex);
             final FindProperty find = findProperty(key, true);
             if (find != null) {
@@ -2993,7 +2993,7 @@
     }
 
     private boolean doesNotHaveCheckArrayKeys(final long longIndex, final Object value, final int callSiteFlags) {
-        if (getMap().containsArrayKeys()) {
+        if (hasDefinedArrayProperties()) {
             final String       key  = JSType.toString(longIndex);
             final FindProperty find = findProperty(key, true);
             if (find != null) {
@@ -3004,6 +3004,15 @@
         return false;
     }
 
+    private boolean hasDefinedArrayProperties() {
+        for (ScriptObject obj = this; obj != null; obj = obj.getProto()) {
+            if (obj.getMap().containsArrayKeys()) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     //value agnostic
     private boolean doesNotHaveEnsureLength(final long longIndex, final long oldLength, final int callSiteFlags) {
         if (longIndex >= oldLength) {

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/nashorn/script/basic/JDK-8201466.js	Mon Apr 23 17:45:05 2018 +0200
@@ -0,0 +1,44 @@
+/*
+ * 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-8201466: Nashorn: defineProperty setters/getters on prototype object ignored with numeric property names
+ *
+ * @test
+ * @run
+ */
+
+var z = {}, s = null, g = null;
+
+Object.defineProperty(z,'0', {
+    get:function(){ g = 2; return 1;},
+    set:function(v){ s = v;}
+});
+
+var x = Object.create(z);
+x[0] = 3;
+
+Assert.assertTrue(x[0] === 1);
+Assert.assertTrue(g === 2);
+Assert.assertTrue(s === 3);
+