diff --git a/completions/tar b/completions/tar
index 45f3ff36..a18fb785 100644
--- a/completions/tar
+++ b/completions/tar
@@ -56,7 +56,7 @@ _tar()
     esac
 
     case $prev in
-        *$ext)
+        *${ext:-$tars})
             # complete on files in tar file
             #
             # get name of tar file from command line