diff --git a/contrib/adc/sudo b/contrib/adc/sudo
index 818db75..47d9641 100755
--- a/contrib/adc/sudo
+++ b/contrib/adc/sudo
@@ -20,4 +20,5 @@ user="$1"; shift
 cmd="$1"; shift
 
 GL_USER=$user; export GL_USER
+[ -x $(dirname $0)/$cmd ] || die "no adc called $cmd"
 exec $(dirname $0)/$cmd "$@"