diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
index 4c2221b..fc4de57 100644
--- a/networking/udhcp/common.c
+++ b/networking/udhcp/common.c
@@ -302,7 +302,7 @@
 {
 	uint8_t *r = udhcp_get_option(packet, code);
 	if (r) {
-		if (r[-1] != 4)
+		if (r[-OPT_DATA + OPT_LEN] != 4)
 			r = NULL;
 	}
 	return r;