diff --git a/sys/net/gnrc/pktbuf_malloc/gnrc_pktbuf_malloc.c b/sys/net/gnrc/pktbuf_malloc/gnrc_pktbuf_malloc.c
index 683044adc0..9eb6335155 100644
--- a/sys/net/gnrc/pktbuf_malloc/gnrc_pktbuf_malloc.c
+++ b/sys/net/gnrc/pktbuf_malloc/gnrc_pktbuf_malloc.c
@@ -210,6 +210,7 @@ void gnrc_pktbuf_hold(gnrc_pktsnip_t *pkt, unsigned int num)
 {
     mutex_lock(&gnrc_pktbuf_mutex);
     while (pkt) {
+        assert(pkt->users + num <= 0xff);
         pkt->users += num;
         pkt = pkt->next;
     }
diff --git a/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c b/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c
index 3c98e8a61d..f1c15279c8 100644
--- a/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c
+++ b/sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c
@@ -213,6 +213,7 @@ void gnrc_pktbuf_hold(gnrc_pktsnip_t *pkt, unsigned int num)
 {
     mutex_lock(&gnrc_pktbuf_mutex);
     while (pkt) {
+        assert(pkt->users + num <= 0xff);
         pkt->users += num;
         pkt = pkt->next;
     }