diff --git a/master.cfg b/master.cfg
index 8b92c95..c2d692d 100644
--- a/master.cfg
+++ b/master.cfg
@@ -661,6 +661,7 @@ def load_config (c):
         factory = globals ()[ "RunTestGDB%s" % btype ]
         b['factory'] = factory (arch_triplet)
         b['canStartBuild'] = DefaultGDBCanStartBuild
+        b['treeStableTimer'] = None
         c['builders'].append (b)
 
 load_config (c)