diff --git a/gpgmymail b/gpgmymail
index 504d10a..7062dcf 100755
--- a/gpgmymail
+++ b/gpgmymail
@@ -56,7 +56,7 @@ def is_message_encrypted(message: email.message.Message) -> bool:
 
     return message.get_content_subtype() == "encrypted"
 
-def get_encoder_from_msg(msg: email.message.Message) -> function:
+def get_encoder_from_msg(msg: email.message.Message) -> typing.Callable:
     """
     Return a suitable encoder function from email.encoders based on an input
     message. If the input message has no Content-Transfer-Encoding header,