diff --git a/lib/Controller/SAMLController.php b/lib/Controller/SAMLController.php
index f0c13b0..3f34007 100644
--- a/lib/Controller/SAMLController.php
+++ b/lib/Controller/SAMLController.php
@@ -354,7 +354,7 @@ class SAMLController extends Controller {
 				$this->userBackend->initializeHomeDir($user->getUID());
 			}
 		} catch (NoUserFoundException $e) {
-			throw new \InvalidArgumentException('User is not valid');
+			throw new \InvalidArgumentException('User "' . $this->userBackend->getCurrentUserId() . '" is not valid');
 		} catch (\Exception $e) {
 			$this->logger->logException($e, ['app' => $this->appName]);
 			$response = new Http\RedirectResponse($this->urlGenerator->linkToRouteAbsolute('user_saml.SAML.notProvisioned'));
diff --git a/lib/UserBackend.php b/lib/UserBackend.php
index f578795..e03c260 100644
--- a/lib/UserBackend.php
+++ b/lib/UserBackend.php
@@ -490,7 +490,7 @@ class UserBackend implements IApacheBackend, UserInterface, IUserBackend {
 		$this->userData->setAttributes($this->session->get('user_saml.samlUserData') ?? []);
 		$uid = $this->userData->getEffectiveUid();
 		if($uid !== '' && $this->userExists($uid)) {
-			$uid = $this->testEncodedObjectGUID($uid);
+			$uid = $this->userData->testEncodedObjectGUID($uid);
 
 			$this->session->set('last-password-confirm', strtotime('+4 year', time()));
 			return $uid;
diff --git a/lib/UserData.php b/lib/UserData.php
index c032d3d..098a9be 100644
--- a/lib/UserData.php
+++ b/lib/UserData.php
@@ -100,7 +100,12 @@ class UserData {
 	 * base64-encoded binary string representing e.g. the objectGUID. Otherwise
 	 *
 	 */
-	protected function testEncodedObjectGUID(string $uid): string {
+	public function testEncodedObjectGUID(string $uid): string {
+		if (preg_match('/[^a-zA-Z0-9=+\/]/', $uid) !== 0) {
+			// certainly not encoded
+			return $uid;
+		}
+
 		$candidate = base64_decode($uid, true);
 		if($candidate === false) {
 			return $uid;
diff --git a/tests/unit/Controller/SAMLControllerTest.php b/tests/unit/Controller/SAMLControllerTest.php
index 856988a..f1d878d 100644
--- a/tests/unit/Controller/SAMLControllerTest.php
+++ b/tests/unit/Controller/SAMLControllerTest.php
@@ -39,7 +39,6 @@ use OCP\IUser;
 use OCP\IUserSession;
 use PHPUnit\Framework\MockObject\MockObject;
 use OCP\Security\ICrypto;
-use PHPUnit\Framework\MockObject\MockObject;
 use Test\TestCase;
 
 class SAMLControllerTest extends TestCase  {
diff --git a/tests/unit/UserBackendTest.php b/tests/unit/UserBackendTest.php
index 0d6ff71..6325091 100644
--- a/tests/unit/UserBackendTest.php
+++ b/tests/unit/UserBackendTest.php
@@ -287,9 +287,4 @@ class UserBackendTest extends TestCase   {
 		$this->userBackend->updateAttributes('ExistingUser', ['email' => 'new@example.com', 'displayname' => 'New Displayname', 'quota' => '']);
 	}
 
-			['aaabbbcc@aa.bbbccdd.eee.ff', 'aaabbbcc@aa.bbbccdd.eee.ff'],
-			['aaabbbcccaa.bbbccdddeee', 'aaabbbcccaa.bbbccdddeee']
-
-
-
 }
diff --git a/tests/unit/UserDataTest.php b/tests/unit/UserDataTest.php
index 7410805..a27f6b2 100644
--- a/tests/unit/UserDataTest.php
+++ b/tests/unit/UserDataTest.php
@@ -58,6 +58,8 @@ class UserDataTest extends TestCase {
 			['EDE70D16-B9D5-4E9A-ABD7-614D17246E3F', 'EDE70D16-B9D5-4E9A-ABD7-614D17246E3F'],
 			['Tm8gY29udmVyc2lvbgo=', 'Tm8gY29udmVyc2lvbgo='],
 			['ASfjU2OYEd69ZgAVF4pePA==', '53E32701-9863-DE11-BD66-0015178A5E3C'],
+			['aaabbbcc@aa.bbbccdd.eee.ff', 'aaabbbcc@aa.bbbccdd.eee.ff'],
+			['aaabbbcccaa.bbbccdddeee', 'aaabbbcccaa.bbbccdddeee']
 		];
 	}