diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index febc9d26f9..eccbc0b1f3 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -2350,6 +2350,7 @@ def mimetype2ext(mt):
         'ttml+xml': 'ttml',
         'x-flv': 'flv',
         'x-mp4-fragmented': 'mp4',
+        'x-ms-sami': 'sami',
         'x-ms-wmv': 'wmv',
         'mpegurl': 'm3u8',
         'x-mpegurl': 'm3u8',