diff --git a/mkmap.sh b/mkmap.sh
index e0f00cc..cd64d42 100755
--- a/mkmap.sh
+++ b/mkmap.sh
@@ -1,8 +1,13 @@
 #!/bin/bash
 
+set -e
+
 DEST=$1
 
 
+[ "$DEST" ] || exit 1
+
+
 GWL=`batctl gwl -n`
 
 SELF=`echo "$GWL" | head -n 1 | sed -r -e 's@^.*MainIF/MAC: [^/]+/([0-9a-f:]+).*$@\1@'`