diff --git a/core.c b/core.c
index 9247b53..cc39dcf 100644
--- a/core.c
+++ b/core.c
@@ -155,7 +155,7 @@
 	return buf;
 }
 
-int mctp_pktbuf_push(struct mctp_pktbuf *pkt, void *data, size_t len)
+int mctp_pktbuf_push(struct mctp_pktbuf *pkt, const void *data, size_t len)
 {
 	void *p;
 
diff --git a/libmctp.h b/libmctp.h
index 76f8ec9..d3c5ed1 100644
--- a/libmctp.h
+++ b/libmctp.h
@@ -65,7 +65,7 @@
 size_t mctp_pktbuf_size(struct mctp_pktbuf *pkt);
 void *mctp_pktbuf_alloc_start(struct mctp_pktbuf *pkt, size_t size);
 void *mctp_pktbuf_alloc_end(struct mctp_pktbuf *pkt, size_t size);
-int mctp_pktbuf_push(struct mctp_pktbuf *pkt, void *data, size_t len);
+int mctp_pktbuf_push(struct mctp_pktbuf *pkt, const void *data, size_t len);
 void *mctp_pktbuf_pop(struct mctp_pktbuf *pkt, size_t len);
 
 /* MCTP core */