--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -2068,16 +2068,17 @@ toolbar#nav-bar {
 
             if crash_count or zombieProcesses:
                 status = 1
 
         finally:
             # cleanup
             if os.path.exists(processLog):
                 os.remove(processLog)
+            self.urlOpts = []
 
         return status
 
     def initializeLooping(self, options):
         """
           This method is used to clear the contents before each run of for loop.
           This method is used for --run-by-dir and --bisect-chunk.
         """