diff --git a/contrib/bash_completion b/contrib/bash_completion
--- a/contrib/bash_completion
+++ b/contrib/bash_completion
@@ -166,4 +166,5 @@
 
 }
 
-complete -o default -F _hg hg
+complete -o bashdefault -o default -F _hg hg 2> /dev/null \
+    || complete -o default -F _hg hg