diff --git a/build/automationutils.py b/build/automationutils.py
index 98c0f3e9293a..a6b6a55ee8d8 100644
--- a/build/automationutils.py
+++ b/build/automationutils.py
@@ -606,6 +606,8 @@ class ShutdownLeaks(object):
           self._logWindow(line)
         elif line[2:10] == "DOCSHELL":
           self._logDocShell(line)
+        elif line.startswith("TEST-START | Shutdown"):
+          self.seenShutdown = True
     elif message['action'] == 'test_start':
       fileName = message['test'].replace("chrome://mochitests/content/browser/", "")
       self.currentTest = {"fileName": fileName, "windows": set(), "docShells": set()}
@@ -614,10 +616,11 @@ class ShutdownLeaks(object):
       if self.currentTest and (self.currentTest["windows"] or self.currentTest["docShells"]):
         self.tests.append(self.currentTest)
       self.currentTest = None
-    elif message['action'] == 'suite_end':
-      self.seenShutdown = True
 
   def process(self):
+    if not self.seenShutdown:
+      self.logger("TEST-UNEXPECTED-FAIL | ShutdownLeaks | process() called before end of test suite")
+
     for test in self._parseLeakingTests():
       for url, count in self._zipLeakedWindows(test["leakedWindows"]):
         self.logger("TEST-UNEXPECTED-FAIL | %s | leaked %d window(s) until shutdown [url = %s]" % (test["fileName"], count, url))
diff --git a/testing/mochitest/runtests.py b/testing/mochitest/runtests.py
index 9374a5284ec0..908370bf1e83 100644
--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -1332,7 +1332,7 @@ class Mochitest(MochitestUtilsMixin):
              symbolsPath=None,
              timeout=-1,
              onLaunch=None,
-             webapprtChrome=False,
+             detectShutdownLeaks=False,
              screenshotOnFail=False,
              testPath=None,
              bisectChunk=None,
@@ -1383,7 +1383,7 @@ class Mochitest(MochitestUtilsMixin):
           testUrl = testUrl.replace("&", "\\&")
         args.append(testUrl)
 
-      if mozinfo.info["debug"] and not webapprtChrome:
+      if detectShutdownLeaks:
         shutdownLeaks = ShutdownLeaks(log.info)
       else:
         shutdownLeaks = None
@@ -1743,6 +1743,9 @@ class Mochitest(MochitestUtilsMixin):
       if options.vmwareRecording:
         self.startVMwareRecording(options);
 
+      # detect shutdown leaks for m-bc runs
+      detectShutdownLeaks = mozinfo.info["debug"] and options.browserChrome and not options.webapprtChrome
+
       log.info("runtests.py | Running tests: start.\n")
       try:
         status = self.runApp(testURL,
@@ -1755,7 +1758,7 @@ class Mochitest(MochitestUtilsMixin):
                              symbolsPath=options.symbolsPath,
                              timeout=timeout,
                              onLaunch=onLaunch,
-                             webapprtChrome=options.webapprtChrome,
+                             detectShutdownLeaks=detectShutdownLeaks,
                              screenshotOnFail=options.screenshotOnFail,
                              testPath=options.testPath,
                              bisectChunk=options.bisectChunk,