diff --git a/gitea-to-ics.py b/gitea-to-ics.py
index 7bb1170..e10d868 100644
--- a/gitea-to-ics.py
+++ b/gitea-to-ics.py
@@ -60,6 +60,8 @@ class Root:
     def todo(self):
         cherrypy.response.headers['WWW-Authenticate'] = \
                 'Basic realm="ICS access"'
+        cherrypy.response.headers['Content-Type'] = \
+                'text/calendar'
         authorization = cherrypy.request.headers.get('Authorization', ':')
         if not authorization:
             raise cherrypy.HTTPError(401, 'Unauthorized')