diff --git a/libavformat/lmlm4.c b/libavformat/lmlm4.c
index aeb5580620..c01304dd45 100644
--- a/libavformat/lmlm4.c
+++ b/libavformat/lmlm4.c
@@ -22,6 +22,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/attributes.h"
 #include "libavutil/intreadwrite.h"
 
 #include "avformat.h"
@@ -110,6 +111,7 @@ static int lmlm4_read_packet(AVFormatContext *s, AVPacket *pkt)
     switch (frame_type) {
     case LMLM4_I_FRAME:
         pkt->flags = AV_PKT_FLAG_KEY;
+        av_fallthrough;
     case LMLM4_P_FRAME:
     case LMLM4_B_FRAME:
         pkt->stream_index = 0;