--- a/dom/cache/StreamControl.cpp
+++ b/dom/cache/StreamControl.cpp
@@ -52,17 +52,18 @@ void StreamControl::CloseReadStreams(con
   }
 
   MOZ_DIAGNOSTIC_ASSERT(closedCount > 0);
 }
 
 void StreamControl::CloseAllReadStreams() {
   AssertOwningThread();
 
-  ReadStreamList::ForwardIterator iter(mReadStreamList);
+  auto readStreamList = mReadStreamList;
+  ReadStreamList::ForwardIterator iter(readStreamList);
   while (iter.HasMore()) {
     iter.GetNext()->CloseStream();
   }
 }
 
 void StreamControl::CloseAllReadStreamsWithoutReporting() {
   AssertOwningThread();