diff --git a/spa/plugins/v4l2/v4l2-utils.c b/spa/plugins/v4l2/v4l2-utils.c
index ca89d9393..1d8add439 100644
--- a/spa/plugins/v4l2/v4l2-utils.c
+++ b/spa/plugins/v4l2/v4l2-utils.c
@@ -1346,6 +1346,7 @@ mmap_init(struct impl *this,
 		}
 
 		b = &port->buffers[i];
+		b->id = i;
 		b->outbuf = buffers[i];
 		b->flags = BUFFER_FLAG_OUTSTANDING;
 		b->h = spa_buffer_find_meta_data(buffers[i], SPA_META_Header, sizeof(*b->h));