diff --git a/content/base/test/chrome/cpows_child.js b/content/base/test/chrome/cpows_child.js
index 8dc79bd497a2..1290d9eb556d 100644
--- a/content/base/test/chrome/cpows_child.js
+++ b/content/base/test/chrome/cpows_child.js
@@ -12,6 +12,9 @@ var is_remote;
     error_reporting_test();
     dom_test();
     xray_test();
+    if (typeof Symbol === "function") {
+      symbol_test();
+    }
     compartment_test();
     regexp_test();
     sync_test();
@@ -119,15 +122,13 @@ function symbol_test()
 {
   let iterator = Symbol.iterator;
   let named = Symbol.for("cpow-test");
-  // let unique = Symbol();
 
   let object = {
     [iterator]: iterator,
     [named]: named,
-    // [unique]: unique,
-    // "unique": unique
   };
-  sendSyncMessage("cpows:symbol_test", {}, object);
+  let test = ['a'];
+  sendSyncMessage("cpows:symbol_test", {}, {object: object, test: test});
 }
 
 // Parent->Child references should go X->parent.privilegedJunkScope->child.privilegedJunkScope->Y
diff --git a/content/base/test/chrome/cpows_parent.xul b/content/base/test/chrome/cpows_parent.xul
index 74c5437c297b..73876f63f016 100644
--- a/content/base/test/chrome/cpows_parent.xul
+++ b/content/base/test/chrome/cpows_parent.xul
@@ -206,10 +206,16 @@
     }
 
     function recvSymbolTest(message) {
-      let object = message.objects;
+      let object = message.objects.object;
       is(object[Symbol.iterator], Symbol.iterator, "Should use Symbol.iterator");
       is(Symbol.keyFor(object[Symbol.for("cpow-test")]), "cpow-test", "Symbols aren't registered correctly");
-      // is(object.unique, object[object.unique], "Unique symbols as ids and values don't seem to work");
+      let symbols = Object.getOwnPropertySymbols(object);
+      is(symbols.length, 2, "Object should have two symbol keys");
+      let test = undefined;
+      for (let x of message.objects.test) {
+        test = x;
+      }
+      is(test, "a", "for .. of iteration should work");
     }
 
     let systemGlobal = this;
@@ -307,7 +313,9 @@
       mm.addMessageListener("cpows:dom_test", recvDomTest);
       mm.addMessageListener("cpows:dom_test_after_gc", recvDomTestAfterGC);
       mm.addMessageListener("cpows:xray_test", recvXrayTest);
-      mm.addMessageListener("cpows:symbol_test", recvSymbolTest);
+      if (typeof Symbol === "function") {
+        mm.addMessageListener("cpows:symbol_test", recvSymbolTest);
+      }
       mm.addMessageListener("cpows:compartment_test", recvCompartmentTest);
       mm.addMessageListener("cpows:regexp_test", recvRegExpTest);
       mm.addMessageListener("cpows:lifetime_test_1", recvLifetimeTest1);
diff --git a/js/ipc/JavaScriptBase.h b/js/ipc/JavaScriptBase.h
index 4ff69ab984ad..a7cf7ff46ee2 100644
--- a/js/ipc/JavaScriptBase.h
+++ b/js/ipc/JavaScriptBase.h
@@ -102,8 +102,8 @@ class JavaScriptBase : public WrapperOwner, public WrapperAnswer, public Base
     }
 
     bool RecvGetPropertyKeys(const uint64_t &objId, const uint32_t &flags,
-                             ReturnStatus *rs, nsTArray<nsString> *names) {
-        return Answer::RecvGetPropertyKeys(ObjectId::deserialize(objId), flags, rs, names);
+                             ReturnStatus *rs, nsTArray<JSIDVariant> *ids) {
+        return Answer::RecvGetPropertyKeys(ObjectId::deserialize(objId), flags, rs, ids);
     }
     bool RecvInstanceOf(const uint64_t &objId, const JSIID &iid,
                           ReturnStatus *rs, bool *instanceof) {
@@ -200,8 +200,8 @@ class JavaScriptBase : public WrapperOwner, public WrapperAnswer, public Base
     }
 
     bool SendGetPropertyKeys(const ObjectId &objId, const uint32_t &flags,
-                             ReturnStatus *rs, nsTArray<nsString> *names) {
-        return Base::SendGetPropertyKeys(objId.serialize(), flags, rs, names);
+                             ReturnStatus *rs, nsTArray<JSIDVariant> *ids) {
+        return Base::SendGetPropertyKeys(objId.serialize(), flags, rs, ids);
     }
     bool SendInstanceOf(const ObjectId &objId, const JSIID &iid,
                         ReturnStatus *rs, bool *instanceof) {
diff --git a/js/ipc/JavaScriptShared.cpp b/js/ipc/JavaScriptShared.cpp
index cff04a719612..38a73cb470e4 100644
--- a/js/ipc/JavaScriptShared.cpp
+++ b/js/ipc/JavaScriptShared.cpp
@@ -440,7 +440,8 @@ JavaScriptShared::toSymbolVariant(JSContext *cx, JS::Symbol *symArg, SymbolVaria
         *symVarp = RegisteredSymbol(autoStr);
         return true;
     }
-    MOZ_CRASH("unique symbols not yet implemented");
+
+    JS_ReportError(cx, "unique symbol can't be used with CPOW");
     return false;
 }
 
diff --git a/js/ipc/PJavaScript.ipdl b/js/ipc/PJavaScript.ipdl
index b17a02ad499d..d8d0254e97e6 100644
--- a/js/ipc/PJavaScript.ipdl
+++ b/js/ipc/PJavaScript.ipdl
@@ -42,7 +42,7 @@ both:
     prio(high) sync ClassName(uint64_t objId) returns (nsString name);
     prio(high) sync RegExpToShared(uint64_t objId) returns (ReturnStatus rs, nsString source, uint32_t flags);
 
-    prio(high) sync GetPropertyKeys(uint64_t objId, uint32_t flags) returns (ReturnStatus rs, nsString[] names);
+    prio(high) sync GetPropertyKeys(uint64_t objId, uint32_t flags) returns (ReturnStatus rs, JSIDVariant[] ids);
     prio(high) sync InstanceOf(uint64_t objId, JSIID iid) returns (ReturnStatus rs, bool instanceof);
     prio(high) sync DOMInstanceOf(uint64_t objId, int prototypeID, int depth) returns (ReturnStatus rs, bool instanceof);
 
diff --git a/js/ipc/WrapperAnswer.cpp b/js/ipc/WrapperAnswer.cpp
index b63013e70b9c..ce8a7eaf4f58 100644
--- a/js/ipc/WrapperAnswer.cpp
+++ b/js/ipc/WrapperAnswer.cpp
@@ -580,7 +580,7 @@ WrapperAnswer::RecvRegExpToShared(const ObjectId &objId, ReturnStatus *rs,
 
 bool
 WrapperAnswer::RecvGetPropertyKeys(const ObjectId &objId, const uint32_t &flags,
-                                   ReturnStatus *rs, nsTArray<nsString> *names)
+                                   ReturnStatus *rs, nsTArray<JSIDVariant> *ids)
 {
     AutoSafeJSContext cx;
     JSAutoRequest request(cx);
@@ -598,11 +598,11 @@ WrapperAnswer::RecvGetPropertyKeys(const ObjectId &objId, const uint32_t &flags,
         return fail(cx, rs);
 
     for (size_t i = 0; i < props.length(); i++) {
-        nsString name;
-        if (!convertIdToGeckoString(cx, props[i], &name))
+        JSIDVariant id;
+        if (!toJSIDVariant(cx, props[i], &id))
             return fail(cx, rs);
 
-        names->AppendElement(name);
+        ids->AppendElement(id);
     }
 
     return ok(rs);
diff --git a/js/ipc/WrapperAnswer.h b/js/ipc/WrapperAnswer.h
index fc3b481f9532..08171528de21 100644
--- a/js/ipc/WrapperAnswer.h
+++ b/js/ipc/WrapperAnswer.h
@@ -55,7 +55,7 @@ class WrapperAnswer : public virtual JavaScriptShared
     bool RecvRegExpToShared(const ObjectId &objId, ReturnStatus *rs, nsString *source, uint32_t *flags);
 
     bool RecvGetPropertyKeys(const ObjectId &objId, const uint32_t &flags,
-                             ReturnStatus *rs, nsTArray<nsString> *names);
+                             ReturnStatus *rs, nsTArray<JSIDVariant> *ids);
     bool RecvInstanceOf(const ObjectId &objId, const JSIID &iid,
                         ReturnStatus *rs, bool *instanceof);
     bool RecvDOMInstanceOf(const ObjectId &objId, const int &prototypeID, const int &depth,
diff --git a/js/ipc/WrapperOwner.cpp b/js/ipc/WrapperOwner.cpp
index 31abb5ce2a3d..adc5df67f67f 100644
--- a/js/ipc/WrapperOwner.cpp
+++ b/js/ipc/WrapperOwner.cpp
@@ -232,7 +232,7 @@ CPOWProxyHandler::ownPropertyKeys(JSContext *cx, HandleObject proxy,
 bool
 WrapperOwner::ownPropertyKeys(JSContext *cx, HandleObject proxy, AutoIdVector &props)
 {
-    return getPropertyKeys(cx, proxy, JSITER_OWNONLY | JSITER_HIDDEN, props);
+    return getPropertyKeys(cx, proxy, JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, props);
 }
 
 bool
@@ -776,8 +776,8 @@ WrapperOwner::getPropertyKeys(JSContext *cx, HandleObject proxy, uint32_t flags,
     ObjectId objId = idOf(proxy);
 
     ReturnStatus status;
-    InfallibleTArray<nsString> names;
-    if (!SendGetPropertyKeys(objId, flags, &status, &names))
+    InfallibleTArray<JSIDVariant> ids;
+    if (!SendGetPropertyKeys(objId, flags, &status, &ids))
         return ipcfail(cx);
 
     LOG_STACK();
@@ -785,11 +785,11 @@ WrapperOwner::getPropertyKeys(JSContext *cx, HandleObject proxy, uint32_t flags,
     if (!ok(cx, status))
         return false;
 
-    for (size_t i = 0; i < names.Length(); i++) {
-        RootedId name(cx);
-        if (!convertGeckoStringToId(cx, names[i], &name))
+    for (size_t i = 0; i < ids.Length(); i++) {
+        RootedId id(cx);
+        if (!fromJSIDVariant(cx, ids[i], &id))
             return false;
-        if (!props.append(name))
+        if (!props.append(id))
             return false;
     }
 
diff --git a/js/ipc/WrapperOwner.h b/js/ipc/WrapperOwner.h
index 215043dfc072..26f19113c72d 100644
--- a/js/ipc/WrapperOwner.h
+++ b/js/ipc/WrapperOwner.h
@@ -146,7 +146,7 @@ class WrapperOwner : public virtual JavaScriptShared
                                     uint32_t *flags) = 0;
 
     virtual bool SendGetPropertyKeys(const ObjectId &objId, const uint32_t &flags,
-                                     ReturnStatus *rs, nsTArray<nsString> *names) = 0;
+                                     ReturnStatus *rs, nsTArray<JSIDVariant> *ids) = 0;
     virtual bool SendInstanceOf(const ObjectId &objId, const JSIID &iid,
                                 ReturnStatus *rs, bool *instanceof) = 0;
     virtual bool SendDOMInstanceOf(const ObjectId &objId, const int &prototypeID, const int &depth,