--- a/xpcom/base/nsCycleCollector.cpp
+++ b/xpcom/base/nsCycleCollector.cpp
@@ -1015,16 +1015,17 @@ class nsCycleCollector : public MemoryMu
     CycleCollectorResults mResults;
     TimeStamp mCollectionStart;
 
     CycleCollectedJSRuntime *mJSRuntime;
 
     ccPhase mIncrementalPhase;
     GCGraph mGraph;
     nsAutoPtr<GCGraphBuilder> mBuilder;
+    nsAutoPtr<NodePool::Enumerator> mCurrNode;
     nsCOMPtr<nsICycleCollectorListener> mListener;
 
     nsIThread* mThread;
 
     nsCycleCollectorParams mParams;
 
     uint32_t mWhiteNodeCount;
 
@@ -2212,37 +2213,37 @@ nsCycleCollector::ForgetSkippable(bool a
 MOZ_NEVER_INLINE void
 nsCycleCollector::MarkRoots()
 {
     TimeLog timeLog;
     AutoRestore<bool> ar(mScanInProgress);
     MOZ_ASSERT(!mScanInProgress);
     mScanInProgress = true;
     MOZ_ASSERT(mIncrementalPhase == GraphBuildingPhase);
-
-    // read the PtrInfo out of the graph that we are building
-    NodePool::Enumerator queue(mGraph.mNodes);
-    while (!queue.IsDone()) {
-        PtrInfo *pi = queue.GetNext();
+    MOZ_ASSERT(mCurrNode);
+
+    while (!mCurrNode->IsDone()) {
+        PtrInfo *pi = mCurrNode->GetNext();
         CC_AbortIfNull(pi);
         mBuilder->Traverse(pi);
-        if (queue.AtBlockEnd()) {
+        if (mCurrNode->AtBlockEnd()) {
             mBuilder->SetLastChild();
         }
     }
     if (mGraph.mRootCount > 0) {
         mBuilder->SetLastChild();
     }
 
     if (mBuilder->RanOutOfMemory()) {
         MOZ_ASSERT(false, "Ran out of memory while building cycle collector graph");
         CC_TELEMETRY(_OOM, true);
     }
 
     mBuilder = nullptr;
+    mCurrNode = nullptr;
     mIncrementalPhase = ScanAndCollectWhitePhase;
     timeLog.Checkpoint("MarkRoots()");
 }
 
 
 ////////////////////////////////////////////////////////////////////////
 // Bacon & Rajan's |ScanRoots| routine.
 ////////////////////////////////////////////////////////////////////////
@@ -2897,16 +2898,17 @@ nsCycleCollector::BeginCollection(ccType
     MOZ_ASSERT(!mScanInProgress);
     mScanInProgress = true;
     mPurpleBuf.SelectPointers(*mBuilder);
     timeLog.Checkpoint("SelectPointers()");
 
     // We've finished adding roots, and everything in the graph is a root.
     mGraph.mRootCount = mGraph.MapCount();
 
+    mCurrNode = new NodePool::Enumerator(mGraph.mNodes);
     mIncrementalPhase = GraphBuildingPhase;
 }
 
 uint32_t
 nsCycleCollector::SuspectedCount()
 {
     CheckThreadSafety();
     return mPurpleBuf.Count();