--- a/hgext3rd/topic/destination.py	Thu Mar 17 09:12:18 2016 -0700
+++ b/hgext3rd/topic/destination.py	Wed Mar 16 12:14:20 2016 -0700
@@ -38,7 +38,7 @@
                               % (top, len(heads)))
         else:
             assert False # that's impossible
-    if orig.func_default: # version above hg-3.7
+    if getattr(orig, 'func_default', ()): # version above hg-3.7
         return orig(repo, action, sourceset, onheadcheck)
     else:
         return orig(repo)