diff --git a/NEWS b/NEWS
index c27ab3d35..11a77af8d 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,8 @@ ver 0.20.19 (not yet released)
   - validate absolute seek time, reject negative values
 * input
   - mms: fix lockup bug and a crash bug
+* decoder
+  - ffmpeg: fix av_register_all() deprecation warning (FFmpeg 4.0)
 * player
   - fix spurious "Not seekable" error when switching radio streams
 * macOS: fix crash bug
diff --git a/src/lib/ffmpeg/Init.cxx b/src/lib/ffmpeg/Init.cxx
index 7f11a72d4..9a7872618 100644
--- a/src/lib/ffmpeg/Init.cxx
+++ b/src/lib/ffmpeg/Init.cxx
@@ -33,6 +33,9 @@ FfmpegInit()
 {
 	av_log_set_callback(FfmpegLogCallback);
 
+#if LIBAVFORMAT_VERSION_INT < AV_VERSION_INT(58, 9, 100)
+	/* deprecated as of FFmpeg 4.0 */
 	av_register_all();
+#endif
 }