diff --git a/test/built-ins/Proxy/ownKeys/return-duplicate-entries-throws.js b/test/built-ins/Proxy/ownKeys/return-duplicate-entries-throws.js
new file mode 100644
index 0000000000000000000000000000000000000000..8bd1512d03fd3fba0a7b9286bf95d28e59cca188
--- /dev/null
+++ b/test/built-ins/Proxy/ownKeys/return-duplicate-entries-throws.js
@@ -0,0 +1,22 @@
+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-proxy-object-internal-methods-and-internal-slots-ownpropertykeys
+description: >
+    The returned list must not contain any duplicate entries.
+info: >
+    [[OwnPropertyKeys]] ( )
+
+    ...
+    9. If trapResult contains any duplicate entries, throw a TypeError exception.
+---*/
+
+var p = new Proxy({}, {
+  ownKeys() {
+    return ["a", "a"];
+  }
+});
+
+assert.throws(TypeError, function() {
+  Object.keys(p);
+});
diff --git a/test/built-ins/Proxy/ownKeys/return-duplicate-symbol-entries-throws.js b/test/built-ins/Proxy/ownKeys/return-duplicate-symbol-entries-throws.js
new file mode 100644
index 0000000000000000000000000000000000000000..dfe27205c0585de085baa9b43ccf0d8fb7186b6c
--- /dev/null
+++ b/test/built-ins/Proxy/ownKeys/return-duplicate-symbol-entries-throws.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-proxy-object-internal-methods-and-internal-slots-ownpropertykeys
+description: >
+    The returned list must not contain any duplicate entries.
+info: >
+    [[OwnPropertyKeys]] ( )
+
+    ...
+    9. If trapResult contains any duplicate entries, throw a TypeError exception.
+---*/
+
+var s = Symbol();
+var p = new Proxy({}, {
+  ownKeys() {
+    return [s, s];
+  }
+});
+
+assert.throws(TypeError, function() {
+  Object.keys(p);
+});