--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -2094,17 +2094,19 @@ class Mochitest(MochitestUtilsMixin):
   def makeTestConfig(self, options):
     "Creates a test configuration file for customizing test execution."
     options.logFile = options.logFile.replace("\\", "\\\\")
     options.testPath = options.testPath.replace("\\", "\\\\")
 
     if "MOZ_HIDE_RESULTS_TABLE" in os.environ and os.environ["MOZ_HIDE_RESULTS_TABLE"] == "1":
       options.hideResultsTable = True
 
-    d = dict((k, v) for k, v in options.__dict__.iteritems() if not k.startswith('log'))
+    d = dict((k, v) for k, v in options.__dict__.items() if
+        (not k.startswith('log_') or
+         not any([k.endswith(fmt) for fmt in commandline.log_formatters.keys()])))
     d['testRoot'] = self.testRoot
     content = json.dumps(d)
 
     with open(os.path.join(options.profilePath, "testConfig.js"), "w") as config:
       config.write(content)
 
   def getTestManifest(self, options):
     if isinstance(options.manifestFile, TestManifest):