diff --git a/configure b/configure
index 51a02393..47eef645 100755
--- a/configure
+++ b/configure
@@ -24,6 +24,7 @@ for x; do
 	--with-ccopts|CFLAGS) CFLAGS=$var;;
 	CPPFLAGS) CPPFLAGS=$var;;
 	--with-hook|--with-hooks|HOOKSCRIPTS) HOOKSCRIPTS=$var;;
+	*) echo "$0: WARNING: unknown option $opt" >&2;;
 	esac
 done