diff --git a/file_packet_provider.c b/file_packet_provider.c
index 4fd768060a..c9ca08e7e3 100644
--- a/file_packet_provider.c
+++ b/file_packet_provider.c
@@ -80,7 +80,7 @@ cap_file_provider_get_modified_block(struct packet_provider_data *prov, const fr
 }
 
 void
-cap_file_provider_set_modified_block(struct packet_provider_data *prov, frame_data *fd, wtap_block_t new_block)
+cap_file_provider_set_modified_block(struct packet_provider_data *prov, frame_data *fd, const wtap_block_t new_block)
 {
   if (!prov->frames_modified_blocks)
     prov->frames_modified_blocks = g_tree_new_full(frame_cmp, NULL, NULL, (GDestroyNotify)wtap_block_unref);