diff --git a/flask_cas/routing.py b/flask_cas/routing.py
index 11b7f24d79..ec9eef6396 100644
--- a/flask_cas/routing.py
+++ b/flask_cas/routing.py
@@ -64,7 +64,7 @@ def login():
         else:
             flask.session.pop(cas_token_session_key, None)
 
-    current_app.logger.debug("Redirecting to: {0}".format(redirect_url))
+    current_app.logger.debug("Redirecting to: {redirect_url}")
 
     return flask.redirect(redirect_url)
 
@@ -100,11 +100,9 @@ def logout():
             dest_url,
         )
     else:
-        redirect_url = create_cas_logout_url(
-            current_app.config["CAS_SERVER"], current_app.config["CAS_LOGOUT_ROUTE"]
-        )
+        redirect_url = create_cas_logout_url(current_app.config["CAS_SERVER"], None)
 
-    current_app.logger.debug("Redirecting to: {0}".format(redirect_url))
+    current_app.logger.debug(f"Redirecting to: {redirect_url}")
     return flask.redirect(redirect_url)