diff --git a/master.cfg b/master.cfg
index 97fee10..600dee3 100644
--- a/master.cfg
+++ b/master.cfg
@@ -949,7 +949,7 @@ def load_config (c):
     c['schedulers'] = []
     for s in config['schedulers']:
         # Ugh :-/.  There should be no special case here...
-        if s['type'] is not 'Nightly':
+        if s['type'] != 'Nightly':
             s['treeStableTimer'] = None
             s['fileIsImportant'] = DefaultGDBfileIsImportant
         else: