diff --git a/src/mod_roster.erl b/src/mod_roster.erl
index 1f42b69e0..6d0b37bc3 100644
--- a/src/mod_roster.erl
+++ b/src/mod_roster.erl
@@ -231,7 +231,7 @@ roster_version(LServer, LUser) ->
     case roster_version_on_db(LServer) of
       true ->
 	  case read_roster_version(LUser, LServer) of
-	    error -> not_found;
+	    error -> <<"not_found">>;
 	    {ok, V} -> V
 	  end;
       false ->