diff --git a/configure b/configure
index 7a74c60132..205eee8cac 100755
--- a/configure
+++ b/configure
@@ -316,6 +316,8 @@ for opt do
   ;;
   --disable-werror) werror="no"
   ;;
+  *) echo "ERROR: unknown option $opt"; show_help="yes"
+  ;;
   esac
 done