diff --git a/scripts/config b/scripts/config
index 9723c7d..f65a44a 100755
--- a/scripts/config
+++ b/scripts/config
@@ -17,6 +17,7 @@
 	                     Set option to "string"
 	--set-val option value
 	                     Set option to value
+	--undefine|-u option Undefine option
 	--state|-s option    Print state of option (n,y,m,undef)
 
 	--enable-after|-E beforeopt option
@@ -73,6 +74,12 @@
 	fi
 }
 
+undef_var() {
+	local name=$1
+
+	sed -ri "/^($name=|# $name is not set)/d" "$FN"
+}
+
 if [ "$1" = "--file" ]; then
 	FN="$2"
 	if [ "$FN" = "" ] ; then
@@ -134,6 +141,9 @@
 		set_var "${CONFIG_}$ARG" "${CONFIG_}$ARG=$1"
 		shift
 		;;
+	--undefine|-u)
+		undef_var "${CONFIG_}$ARG"
+		;;
 
 	--state|-s)
 		if grep -q "# ${CONFIG_}$ARG is not set" $FN ; then