diff --git a/animetosho2mks.py b/animetosho2mks.py
index a42916d..7e33d04 100755
--- a/animetosho2mks.py
+++ b/animetosho2mks.py
@@ -3,7 +3,6 @@
 from subprocess import run
 from tqdm import tqdm
 import glob
-import mimetypes
 import os.path
 
 
@@ -26,9 +25,6 @@ class SubtitleTrack:
 class Attachment:
     def __init__(self, filename):
         self.filename = filename
-        self.mimetype = mimetypes.guess_type(self.filename)[0]
-        if self.mimetype is None:
-            raise Exception(f"Cannot guess mimetype of attachment {self.mimetype}")
 
 
 class AnimeToshoFile:
@@ -64,7 +60,7 @@ class AnimeToshoFile:
             command.extend(
                 [
                     "--attachment-mime-type",
-                    attachment.mimetype,
+                    "font/sfnt",
                     "--attach-file",
                     os.path.join(self.base, "attachments", attachment.filename),
                 ]