--- a/netwerk/base/nsStandardURL.cpp
+++ b/netwerk/base/nsStandardURL.cpp
@@ -261,16 +261,17 @@ nsStandardURL::nsStandardURL(bool aSuppo
         gInitialized = true;
         InitGlobalObjects();
     }
 
     // default parser in case nsIStandardURL::Init is never called
     mParser = net_GetStdURLParser();
 
 #ifdef DEBUG_DUMP_URLS_AT_SHUTDOWN
+    memset(&mDebugCList, 0, sizeof(mDebugCList));
     if (NS_IsMainThread()) {
         if (aTrackURL) {
             PR_APPEND_LINK(&mDebugCList, &gAllURLs);
         } else {
             PR_INIT_CLIST(&mDebugCList);
         }
     }
 #endif