diff --git a/yt_dlp/postprocessor/ffmpeg.py b/yt_dlp/postprocessor/ffmpeg.py
index 7c904417baef..24b223707efe 100644
--- a/yt_dlp/postprocessor/ffmpeg.py
+++ b/yt_dlp/postprocessor/ffmpeg.py
@@ -349,6 +349,8 @@ def make_args(file, args, name, number):
                     keys.append('')
             args += self._configuration_args(self.basename, keys)
             if name == 'i':
+                if determine_ext(file) == 'ass':
+                    args.append('-fix_sub_duration')
                 args.append('-i')
             return (
                 [encodeArgument(arg) for arg in args]