diff --git a/cps/helper.py b/cps/helper.py
index 0c38b684..f7bda696 100755
--- a/cps/helper.py
+++ b/cps/helper.py
@@ -266,6 +266,7 @@ def get_valid_filename(value, replace_whitespace=True):
     """
     if value[-1:] == u'.':
         value = value[:-1]+u'_'
+    value = value.replace("/", "_").replace(":", "_")
     if use_unidecode:
         value=(unidecode.unidecode(value)).strip()
     else: