diff --git a/eventtools/models/rule.py b/eventtools/models/rule.py
index 0ea323a7..a5ab132d 100644
--- a/eventtools/models/rule.py
+++ b/eventtools/models/rule.py
@@ -110,7 +110,7 @@ def get_rrule(self, dtstart):
                 .replace("%-nthday%", "%s%s" % (minus_n, weekday))
             try:
                 return rrule.rrulestr(str(cr), dtstart=dtstart)
-            except: #Except what?
+            except ValueError: # eg. unsupported property 
                 pass
         params = self.get_params()
         frequency = 'rrule.%s' % self.frequency