diff --git a/libmpdemux/muxer_lavf.c b/libmpdemux/muxer_lavf.c
index 0fe8984964..e83ef4b924 100644
--- a/libmpdemux/muxer_lavf.c
+++ b/libmpdemux/muxer_lavf.c
@@ -24,6 +24,8 @@
 #endif
 #include "libavutil/avstring.h"
 
+enum PixelFormat imgfmt2pixfmt(int fmt);
+
 extern const struct AVCodecTag *mp_wav_taglists[];
 extern const struct AVCodecTag *mp_bmp_taglists[];