diff --git a/server.py b/server.py
index cbeac36..b52e990 100644
--- a/server.py
+++ b/server.py
@@ -45,7 +45,7 @@ def gencert():
         for file_name, data in [('cert.pem', io.BytesIO(crypto.dump_certificate(crypto.FILETYPE_PEM, cert))),
                                 ('privkey.pem', io.BytesIO(crypto.dump_privatekey(crypto.FILETYPE_PEM, k)))]:
             zip_file.writestr(file_name, data.getvalue())
-    return zip_buffer.getvalue()
+    return Response(zip_buffer.getvalue(), mimetype="application/zip")
 @app.route("/style.css")
 def style():
     return send_file("style.css")