diff --git a/tool/bisect.sh b/tool/bisect.sh
index 07d7bdbb2b..d486c9cfc6 100755
--- a/tool/bisect.sh
+++ b/tool/bisect.sh
@@ -38,7 +38,7 @@ case $1 in
     echo foo bar
     ;;
   * )
-    echo unknown command "'$cmd'" 1>&2
+    echo unknown command "'$1'" 1>&2
     exit 1
     ;;
 esac