--- a/hgweb.cgi
+++ b/hgweb.cgi
@@ -3,6 +3,8 @@
 # An example CGI script to use hgweb, edit as necessary
 
 import cgitb, os, sys
+cgitb.enable()
+
 # sys.path.insert(0, "/path/to/python/lib") # if not a system-wide install
 from mercurial import hgweb