diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index ed5d436c76d..a665c641b22 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -627,44 +627,8 @@ DefinePropertyOnTypedArray(JSContext* cx, HandleObject obj, HandleId id,
     MOZ_ASSERT(IsAnyTypedArray(obj));
     // Steps 3.a-c.
     uint64_t index;
-    if (IsTypedArrayIndex(id, &index)) {
-        // These are all substeps of 3.c.
-        // Steps i-vi.
-        // We (wrongly) ignore out of range defines with a value.
-        if (index >= AnyTypedArrayLength(obj))
-            return result.succeed();
-
-        // Step vii.
-        if (desc.isAccessorDescriptor())
-            return result.fail(JSMSG_CANT_REDEFINE_PROP);
-
-        // Step viii.
-        if (desc.hasConfigurable() && desc.configurable())
-            return result.fail(JSMSG_CANT_REDEFINE_PROP);
-
-        // Step ix.
-        if (desc.hasEnumerable() && !desc.enumerable())
-            return result.fail(JSMSG_CANT_REDEFINE_PROP);
-
-        // Step x.
-        if (desc.hasWritable() && !desc.writable())
-            return result.fail(JSMSG_CANT_REDEFINE_PROP);
-
-        // Step xi.
-        if (desc.hasValue()) {
-            double d;
-            if (!ToNumber(cx, desc.value(), &d))
-                return false;
-
-            if (obj->is<TypedArrayObject>())
-                TypedArrayObject::setElement(obj->as<TypedArrayObject>(), index, d);
-            else
-                SharedTypedArrayObject::setElement(obj->as<SharedTypedArrayObject>(), index, d);
-        }
-
-        // Step xii.
-        return result.succeed();
-    }
+    if (IsTypedArrayIndex(id, &index))
+        return DefineTypedArrayElement(cx, obj, index, desc, result);
 
     // Step 4.
     return DefinePropertyOnObject(cx, obj.as<NativeObject>(), id, desc, result);
diff --git a/js/src/vm/NativeObject.cpp b/js/src/vm/NativeObject.cpp
index 9398adb6e5c..f86a6b6bb87 100644
--- a/js/src/vm/NativeObject.cpp
+++ b/js/src/vm/NativeObject.cpp
@@ -1302,10 +1302,13 @@ js::NativeDefineProperty(ExclusiveContext* cx, HandleNativeObject obj, HandleId
                 return result.fail(JSMSG_CANT_DEFINE_PAST_ARRAY_LENGTH);
         }
     } else if (IsAnyTypedArray(obj)) {
-        // Don't define new indexed properties on typed arrays.
+        // 9.4.5.3 step 3. Indexed properties of typed arrays are special.
         uint64_t index;
-        if (IsTypedArrayIndex(id, &index))
-            return result.succeed();
+        if (IsTypedArrayIndex(id, &index)) {
+            if (!cx->shouldBeJSContext())
+                return false;
+            return DefineTypedArrayElement(cx->asJSContext(), obj, index, desc_, result);
+        }
     }
 
     Rooted<PropertyDescriptor> desc(cx, desc_);
diff --git a/js/src/vm/TypedArrayObject.cpp b/js/src/vm/TypedArrayObject.cpp
index 7a32a41e601..827e9af3128 100644
--- a/js/src/vm/TypedArrayObject.cpp
+++ b/js/src/vm/TypedArrayObject.cpp
@@ -2105,6 +2105,51 @@ js::StringIsTypedArrayIndex(const char16_t* s, size_t length, uint64_t* indexp);
 template bool
 js::StringIsTypedArrayIndex(const Latin1Char* s, size_t length, uint64_t* indexp);
 
+/* ES6 draft rev 34 (2015 Feb 20) 9.4.5.3 [[DefineOwnProperty]] step 3.c. */
+bool
+js::DefineTypedArrayElement(JSContext *cx, HandleObject obj, uint64_t index,
+                            Handle<PropertyDescriptor> desc, ObjectOpResult &result)
+{
+    MOZ_ASSERT(IsAnyTypedArray(obj));
+
+    // These are all substeps of 3.c.
+    // Steps i-vi.
+    // We (wrongly) ignore out of range defines with a value.
+    if (index >= AnyTypedArrayLength(obj))
+        return result.succeed();
+
+    // Step vii.
+    if (desc.isAccessorDescriptor())
+        return result.fail(JSMSG_CANT_REDEFINE_PROP);
+
+    // Step viii.
+    if (desc.hasConfigurable() && desc.configurable())
+        return result.fail(JSMSG_CANT_REDEFINE_PROP);
+
+    // Step ix.
+    if (desc.hasEnumerable() && !desc.enumerable())
+        return result.fail(JSMSG_CANT_REDEFINE_PROP);
+
+    // Step x.
+    if (desc.hasWritable() && !desc.writable())
+        return result.fail(JSMSG_CANT_REDEFINE_PROP);
+
+    // Step xi.
+    if (desc.hasValue()) {
+        double d;
+        if (!ToNumber(cx, desc.value(), &d))
+            return false;
+
+        if (obj->is<TypedArrayObject>())
+            TypedArrayObject::setElement(obj->as<TypedArrayObject>(), index, d);
+        else
+            SharedTypedArrayObject::setElement(obj->as<SharedTypedArrayObject>(), index, d);
+    }
+
+    // Step xii.
+    return result.succeed();
+}
+
 /* JS Friend API */
 
 JS_FRIEND_API(bool)
diff --git a/js/src/vm/TypedArrayObject.h b/js/src/vm/TypedArrayObject.h
index 04f6ec129d2..6822e2ade09 100644
--- a/js/src/vm/TypedArrayObject.h
+++ b/js/src/vm/TypedArrayObject.h
@@ -277,6 +277,14 @@ IsTypedArrayIndex(jsid id, uint64_t* indexp)
     return StringIsTypedArrayIndex(s, length, indexp);
 }
 
+/*
+ * Implements [[DefineOwnProperty]] for TypedArrays and SharedTypedArrays
+ * when the property key is a TypedArray index.
+ */
+bool
+DefineTypedArrayElement(JSContext *cx, HandleObject arr, uint64_t index,
+                        Handle<PropertyDescriptor> desc, ObjectOpResult &result);
+
 static inline unsigned
 TypedArrayShift(Scalar::Type viewType)
 {