diff --git a/pisi/graph.py b/pisi/graph.py
index 48ac928e..c419f90c 100644
--- a/pisi/graph.py
+++ b/pisi/graph.py
@@ -16,7 +16,7 @@ ver = sys.version_info
 if ver[0] <= 2 and ver[1] < 4:
     from sets import Set as set
 
-class CycleError:
+class CycleError(Exception):
     pass
 
 class digraph(object):