diff --git a/ripple1d/conflate/rasfim.py b/ripple1d/conflate/rasfim.py
index c1b43f58..e654e0c5 100644
--- a/ripple1d/conflate/rasfim.py
+++ b/ripple1d/conflate/rasfim.py
@@ -2,6 +2,7 @@
 
 import json
 import logging
+import os
 from collections import OrderedDict
 from typing import List, Tuple