--- a/testing/web-platform/tests/tools/wptrunner/wptrunner/executors/executormarionette.py
+++ b/testing/web-platform/tests/tools/wptrunner/wptrunner/executors/executormarionette.py
@@ -154,18 +154,23 @@ class MarionetteProtocol(Protocol):
             # The runner window probably changed id but we can restore it
             # This isn't supposed to happen, but marionette ids are not yet stable
             # We assume that the first handle returned corresponds to the runner,
             # but it hopefully doesn't matter too much if that assumption is
             # wrong since we reload the runner in that tab anyway.
             runner_handle = handles.pop(0)
 
         for handle in handles:
-            self.marionette.switch_to_window(handle)
-            self.marionette.close()
+            try:
+                self.marionette.switch_to_window(handle)
+                self.marionette.close()
+            except errors.NoSuchWindowException:
+                # We might have raced with the previous test to close this
+                # window, skip it.
+                pass
 
         self.marionette.switch_to_window(runner_handle)
         if runner_handle != self.runner_handle:
             self.load_runner(protocol)
 
     def wait(self):
         socket_timeout = self.marionette.client.sock.gettimeout()
         if socket_timeout: