diff --git a/gen.sh b/gen.sh
index d0dca0a..086c447 100755
--- a/gen.sh
+++ b/gen.sh
@@ -4,7 +4,7 @@
 assert_tools () {
 	err=0
 	while test $# -gt 0; do
-		command "$1" >/dev/null 2>/dev/null || {
+		command -v "$1" >/dev/null 2>/dev/null || {
 			>&2 printf "tool missing: $1\n"
 			err=$(( $err + 1 ))
 		}