diff --git a/src/packet.c b/src/packet.c
index 2a43dce6..e8089082 100644
--- a/src/packet.c
+++ b/src/packet.c
@@ -39,7 +39,7 @@ pkt_destroy(th_pkt_t *pkt)
  * suppoed to take care of)
  */
 th_pkt_t *
-pkt_alloc(void *data, size_t datalen, int64_t pts, int64_t dts)
+pkt_alloc(const void *data, size_t datalen, int64_t pts, int64_t dts)
 {
   th_pkt_t *pkt;
 
diff --git a/src/packet.h b/src/packet.h
index 9d80c80f..57ed5213 100644
--- a/src/packet.h
+++ b/src/packet.h
@@ -71,7 +71,7 @@ void pkt_ref_inc_poly(th_pkt_t *pkt, int n);
 
 void pktref_clear_queue(struct th_pktref_queue *q);
 
-th_pkt_t *pkt_alloc(void *data, size_t datalen, int64_t pts, int64_t dts);
+th_pkt_t *pkt_alloc(const void *data, size_t datalen, int64_t pts, int64_t dts);
 
 th_pkt_t *pkt_merge_global(th_pkt_t *pkt);