diff --git a/python/planout/ops/utils.py b/python/planout/ops/utils.py
index 710cef9..84c6ef4 100644
--- a/python/planout/ops/utils.py
+++ b/python/planout/ops/utils.py
@@ -92,7 +92,7 @@ def pretty(params):
             try:
                 # if an op is invalid, we may not be able to pretty print it
                 my_pretty = Operators.operatorInstance(params).pretty()
-            except:
+            except AssertionError:
                 my_pretty = params
             return my_pretty
         elif type(params) is list: