diff --git a/browser/components/preferences/in-content/tests/browser.ini b/browser/components/preferences/in-content/tests/browser.ini
index 3003b3293f5e..65091f957080 100644
--- a/browser/components/preferences/in-content/tests/browser.ini
+++ b/browser/components/preferences/in-content/tests/browser.ini
@@ -8,7 +8,7 @@ support-files =
 [browser_bug731866.js]
 [browser_connection.js]
 [browser_healthreport.js]
-skip-if = (!healthreport) || (os == 'linux' && debug)
+skip-if = !healthreport || (os == 'linux' && debug)
 [browser_privacypane_1.js]
 [browser_privacypane_3.js]
 [browser_privacypane_5.js]
diff --git a/browser/components/preferences/tests/browser.ini b/browser/components/preferences/tests/browser.ini
index 585ec6a8fccf..c78f160ba8cc 100644
--- a/browser/components/preferences/tests/browser.ini
+++ b/browser/components/preferences/tests/browser.ini
@@ -8,7 +8,7 @@ support-files =
 [browser_bug705422.js]
 [browser_chunk_permissions.js]
 [browser_healthreport.js]
-skip-if = (!healthreport) || (os == 'linux' && debug)
+skip-if = !healthreport || (os == 'linux' && debug)
 [browser_permissions.js]
 [browser_privacypane_1.js]
 [browser_privacypane_3.js]
diff --git a/testing/mozbase/manifestdestiny/manifestparser/manifestparser.py b/testing/mozbase/manifestdestiny/manifestparser/manifestparser.py
index 907fc7be5867..adc59a769aec 100755
--- a/testing/mozbase/manifestdestiny/manifestparser/manifestparser.py
+++ b/testing/mozbase/manifestdestiny/manifestparser/manifestparser.py
@@ -85,7 +85,7 @@ class neq_op_token(object):
 class not_op_token(object):
     "!"
     def nud(self, parser):
-        return not parser.expression()
+        return not parser.expression(100)
 
 class and_op_token(object):
     "&&"
diff --git a/testing/mozbase/manifestdestiny/tests/test_expressionparser.py b/testing/mozbase/manifestdestiny/tests/test_expressionparser.py
index 448facea8709..d8a1c310ef38 100755
--- a/testing/mozbase/manifestdestiny/tests/test_expressionparser.py
+++ b/testing/mozbase/manifestdestiny/tests/test_expressionparser.py
@@ -78,5 +78,18 @@ class ExpressionParserTest(unittest.TestCase):
         self.assertTrue(parse('"string with #" == "string with #" # really, it does'))
         self.assertTrue(parse('"string with #" != "string with # but not the same" # no match!'))
 
+    def test_not(self):
+        """
+        Test the ! operator.
+        """
+        self.assertTrue(parse("!false"))
+        self.assertTrue(parse("!(false)"))
+        self.assertFalse(parse("!true"))
+        self.assertFalse(parse("!(true)"))
+        self.assertTrue(parse("!true || true)"))
+        self.assertTrue(parse("true || !true)"))
+        self.assertFalse(parse("!true && true"))
+        self.assertFalse(parse("true && !true"))
+
 if __name__ == '__main__':
     unittest.main()