diff --git a/gajim/common/helpers.py b/gajim/common/helpers.py
index 97840abf6..a8d43a9a9 100644
--- a/gajim/common/helpers.py
+++ b/gajim/common/helpers.py
@@ -431,6 +431,8 @@ def get_uf_sub(sub):
         uf_sub = _('From')
     elif sub == 'both':
         uf_sub = _('Both')
+    elif sub is None:
+        uf_sub = _('Unknown')
     else:
         uf_sub = sub