diff --git a/src/main/php/web/auth/Flow.class.php b/src/main/php/web/auth/Flow.class.php
index 9866823..4d7190e 100755
--- a/src/main/php/web/auth/Flow.class.php
+++ b/src/main/php/web/auth/Flow.class.php
@@ -6,6 +6,19 @@ abstract class Flow {
   const FRAGMENT= '_';
 
   private $url= null;
+  protected $namespace;
+
+  /**
+   * Sets session namespace for this flow. Used to prevent conflicts
+   * in session state with multiple OAuth flows in place.
+   *
+   * @param  string $namespace
+   * @return self
+   */
+  public function namespaced($namespace) {
+    $this->namespace= $namespace;
+    return $this;
+  }
 
   /**
    * Targets a given URL
diff --git a/src/main/php/web/auth/cas/CasFlow.class.php b/src/main/php/web/auth/cas/CasFlow.class.php
index 8b0c249..b7007c6 100755
--- a/src/main/php/web/auth/cas/CasFlow.class.php
+++ b/src/main/php/web/auth/cas/CasFlow.class.php
@@ -8,8 +8,6 @@
 use web\{Cookie, Error, Filter};
 
 class CasFlow extends Flow {
-  const SESSION_KEY = 'cas::flow';
-
   private $sso;
 
   /**
@@ -19,6 +17,7 @@ class CasFlow extends Flow {
    */
   public function __construct($sso) {
     $this->sso= rtrim($sso, '/');
+    $this->namespace= 'cas::flow';
   }
 
   /**
@@ -44,7 +43,7 @@ protected function validate($ticket, $service) {
    * @return var
    */
   public function authenticate($request, $response, $session) {
-    $state= $session->value(self::SESSION_KEY);
+    $state= $session->value($this->namespace);
     if (isset($state['username'])) return $state;
 
     // If no ticket is present, redirect to SSO. Otherwise, validate ticket,
@@ -104,7 +103,7 @@ public function authenticate($request, $response, $session) {
 
     // Success-oriented
     if ($user= $result['user'] ?? null) {
-      $session->register(self::SESSION_KEY, $user);
+      $session->register($this->namespace, $user);
       $session->transmit($response);
       $this->finalize($response, $service);
       return null;
diff --git a/src/main/php/web/auth/oauth/OAuthFlow.class.php b/src/main/php/web/auth/oauth/OAuthFlow.class.php
index d01d72c..83db688 100755
--- a/src/main/php/web/auth/oauth/OAuthFlow.class.php
+++ b/src/main/php/web/auth/oauth/OAuthFlow.class.php
@@ -4,7 +4,7 @@
 use web\auth\{Flow, UserInfo, AuthenticationError};
 
 abstract class OAuthFlow extends Flow {
-  protected $callback, $namespace;
+  protected $callback;
 
   /** @return ?util.URI */
   public function callback() { return $this->callback; }
@@ -15,18 +15,6 @@ public function calling($callback): self {
     return $this;
   }
 
-  /**
-   * Sets session namespace for this flow. Used to prevent conflicts
-   * in session state with multiple OAuth flows in place.
-   *
-   * @param  string $namespace
-   * @return self
-   */
-  public function namespaced($namespace) {
-    $this->namespace= $namespace;
-    return $this;
-  }
-
   /**
    * Returns user info which fetched from the given endpoint using the
    * authorized OAuth client
diff --git a/src/test/php/web/auth/unittest/CasFlowTest.class.php b/src/test/php/web/auth/unittest/CasFlowTest.class.php
index 5417de0..0365e93 100755
--- a/src/test/php/web/auth/unittest/CasFlowTest.class.php
+++ b/src/test/php/web/auth/unittest/CasFlowTest.class.php
@@ -11,6 +11,7 @@
 use web\{Error, Request, Response};
 
 class CasFlowTest extends FlowTest {
+  const SNS     = 'cas::flow';
   const SSO     = 'https://example.com/sso';
   const SERVICE = 'https://service.example.com';
   const TICKET  = 'ST-1856339-aA5Yuvrxzpv8Tau1cYQ7';
@@ -147,7 +148,29 @@ public function validate($ticket, $service) {
     $this->authenticate($fixture, '/?ticket='.self::TICKET, $session);
     Assert::equals(
       ['username' => 'test'],
-      $session->value(CasFlow::SESSION_KEY)
+      $session->value(self::SNS)
+    );
+  }
+
+  #[Test, Values(['cas::flow', 'flow'])]
+  public function session_namespace($namespace) {
+    $fixture= new class(self::SSO) extends CasFlow {
+      public function validate($ticket, $service) {
+        return CasFlowTest::response('
+          <cas:serviceResponse xmlns:cas="http://www.yale.edu/tp/cas">
+            <cas:authenticationSuccess>
+              <cas:user>test</cas:user>
+            </cas:authenticationSuccess>
+          </cas:serviceResponse>
+        ');
+      }
+    };
+    $session= (new ForTesting())->create();
+
+    $this->authenticate($fixture->namespaced($namespace), '/?ticket='.self::TICKET, $session);
+    Assert::equals(
+      ['username' => 'test'],
+      $session->value($namespace)
     );
   }
 
@@ -173,7 +196,7 @@ public function validate($ticket, $service) {
     $this->authenticate($fixture, '/?ticket='.self::TICKET, $session);
     Assert::equals(
       ['username' => 'test', 'givenName' => 'John Doe', 'email' => 'jdoe@example.org'],
-      $session->value(CasFlow::SESSION_KEY)
+      $session->value(self::SNS)
     );
   }
 
@@ -183,7 +206,7 @@ public function returns_user_in_final_step() {
 
     $fixture= new CasFlow(self::SSO);
     $session= (new ForTesting())->create();
-    $session->register(CasFlow::SESSION_KEY, $user);
+    $session->register(self::SNS, $user);
 
     $req= new Request(new TestInput('GET', '/'));
     $res= new Response(new TestOutput());