diff --git a/pisi/util.py b/pisi/util.py
index f94cc95f..718dd142 100644
--- a/pisi/util.py
+++ b/pisi/util.py
@@ -265,7 +265,7 @@ def get_file_hashes(top, exclude_prefix=None, removePrefix=None):
         try:
             return func(f)
         except FileError:
-            return "0"
+            return None
 
     # also handle single files
     if os.path.isfile(top):