diff --git a/flask_cas/routing.py b/flask_cas/routing.py
index dc2ee5d6..cb2b532c 100644
--- a/flask_cas/routing.py
+++ b/flask_cas/routing.py
@@ -8,7 +8,7 @@ from urllib.error import URLError
 from urllib.request import urlopen
 
 import flask
-from flask import current_app
+from flask import current_app, request
 from xmltodict import parse
 
 from .cas_urls import create_cas_login_url
@@ -86,23 +86,27 @@ def logout():
     flask.session.pop(cas_attributes_session_key, None)
     flask.session.pop(cas_token_session_key, None)  # added by EV
     flask.session.pop("CAS_EDT_ID", None)  # added by EV
-
     cas_after_logout = current_app.config.get("CAS_AFTER_LOGOUT")
-    if cas_after_logout:
-        # If config starts with http, use it as dest URL.
-        # Else, build Flask URL
-        dest_url = (
-            cas_after_logout
-            if cas_after_logout.startswith("http")
-            else flask.url_for(cas_after_logout, _external=True)
-        )
-        redirect_url = create_cas_logout_url(
-            current_app.config["CAS_SERVER"],
-            current_app.config["CAS_LOGOUT_ROUTE"],
-            dest_url,
-        )
+    cas_logout_route = current_app.config.get("CAS_LOGOUT_ROUTE")
+    cas_server = current_app.config.get("CAS_SERVER")
+    if cas_server:
+        if cas_after_logout and cas_logout_route:
+            # If config starts with http, use it as dest URL.
+            # Else, build Flask URL
+            dest_url = (
+                cas_after_logout
+                if cas_after_logout.startswith("http")
+                else flask.url_for(cas_after_logout, _external=True)
+            )
+            redirect_url = create_cas_logout_url(
+                cas_server,
+                cas_logout_route,
+                dest_url,
+            )
+        else:
+            redirect_url = create_cas_logout_url(cas_server, None)
     else:
-        redirect_url = create_cas_logout_url(current_app.config["CAS_SERVER"], None)
+        redirect_url = request.root_url
 
     current_app.logger.debug(f"cas.logout: redirecting to {redirect_url}")
     return flask.redirect(redirect_url)
@@ -134,10 +138,10 @@ def validate(ticket):
         ticket,
     )
 
-    current_app.logger.debug("Making GET request to {0}".format(cas_validate_url))
+    current_app.logger.debug(f"Making GET request to {cas_validate_url}")
 
     xml_from_dict = {}
-    isValid = False
+    is_valid = False
 
     if current_app.config.get("CAS_SSL_VERIFY"):
         ssl_context = ssl.SSLContext()
@@ -161,7 +165,7 @@ def validate(ticket):
             .decode("utf8", "ignore")
         )
         xml_from_dict = parse(xmldump)
-        isValid = (
+        is_valid = (
             True
             if "cas:authenticationSuccess" in xml_from_dict["cas:serviceResponse"]
             else False
@@ -176,7 +180,7 @@ def validate(ticket):
             "erreur connexion au serveur CAS: vérifiez le certificat SSL"
         )
 
-    if isValid:
+    if is_valid:
         current_app.logger.debug("valid")
         xml_from_dict = xml_from_dict["cas:serviceResponse"][
             "cas:authenticationSuccess"
@@ -207,4 +211,4 @@ def validate(ticket):
     else:
         current_app.logger.debug("invalid")
 
-    return isValid
+    return is_valid