--- a/nashorn/src/jdk/nashorn/internal/objects/NativeArray.java	Fri Sep 27 16:59:01 2013 +0200
+++ b/nashorn/src/jdk/nashorn/internal/objects/NativeArray.java	Fri Sep 27 17:00:37 2013 +0200
@@ -860,9 +860,12 @@
             return new NativeArray(sobj.getArray().slice(k, finale));
         }
 
-        final NativeArray copy = new NativeArray(0);
+        // Construct array with proper length to have a deleted filter on undefined elements
+        final NativeArray copy = new NativeArray(finale - k);
         for (long n = 0; k < finale; n++, k++) {
-            copy.defineOwnProperty(ArrayIndex.getArrayIndex(n), sobj.get(k));
+            if (sobj.has(k)) {
+                copy.defineOwnProperty(ArrayIndex.getArrayIndex(n), sobj.get(k));
+            }
         }
 
         return copy;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nashorn/test/script/basic/JDK-8025520.js	Fri Sep 27 17:00:37 2013 +0200
@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2010, 2013, 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-8025520: Array.prototype.slice should only copy defined elements
+ *
+ * @test
+ * @run
+ */
+
+var s = Array.prototype.slice.call({length: 6, 3: 1}, 2, 5);
+
+if (s.length != 3) {
+    fail("s.length != 3");
+}
+if (0 in s) {
+    fail("0 in s");
+}
+if (s.hasOwnProperty(0)) {
+    fail("s.hasOwnProperty(0)");
+}
+if (s[1] !== 1) {
+    fail("s[1] !== 1");
+}
+if (2 in s) {
+    fail("2 in s");
+}
+if (s.hasOwnProperty(2)) {
+    fail("s.hasOwnProperty(2)");
+}