diff --git a/slirp/bootp.c b/slirp/bootp.c
index 56caf70..9f0652f 100644
--- a/slirp/bootp.c
+++ b/slirp/bootp.c
@@ -238,7 +238,7 @@
 
 void bootp_input(struct mbuf *m)
 {
-    struct bootp_t *bp = (struct bootp_t *)m->m_data;
+    struct bootp_t *bp = mtod(m, struct bootp_t *);
 
     if (bp->bp_op == BOOTP_REQUEST) {
         bootp_reply(bp);