diff --git a/overlay/overlay b/overlay/overlay
index 8c3ac99..a32f218 100755
--- a/overlay/overlay
+++ b/overlay/overlay
@@ -27,7 +27,7 @@
     umount $o_lowerdir
     if [ -z "$o_options" ]
     then
-        echo $o_lowerdir is not an overlay
+        echo >&2 $o_lowerdir is not an overlay
         exit 1
     else
         echo "${o_options}" |