diff --git a/fftools/ffmpeg_enc.c b/fftools/ffmpeg_enc.c
index 0f7d961472..a595912933 100644
--- a/fftools/ffmpeg_enc.c
+++ b/fftools/ffmpeg_enc.c
@@ -728,7 +728,7 @@ static int encode_frame(OutputFile *of, OutputStream *ost, AVFrame *frame,
         }
     }
 
-    av_assert0(0);
+    av_unreachable("encode_frame() loop should return");
 }
 
 static enum AVPictureType forced_kf_apply(void *logctx, KeyframeForceCtx *kf,