diff --git a/src/Control/SAMLController.php b/src/Control/SAMLController.php
index cc4eff7..7146340 100644
--- a/src/Control/SAMLController.php
+++ b/src/Control/SAMLController.php
@@ -156,8 +156,6 @@ public function acs()
             return $this->getRedirect();
         }
 
-        $this->extend('updateGuid', $guid);
-
         $attributes = $auth->getAttributes();
 
         // Allows setups that map GUID (email format) to email {@see SAMLConfiguration::$expose_guid_as_attribute}.
@@ -166,6 +164,7 @@ public function acs()
         }
 
         $this->extend('updateAttributes', $attributes);
+        $this->extend('updateGuid', $guid);
 
         $fieldToClaimMap = array_flip(Member::config()->claims_field_mappings);
 
diff --git a/src/Helpers/SAMLHelper.php b/src/Helpers/SAMLHelper.php
index 6681542..e6273ea 100644
--- a/src/Helpers/SAMLHelper.php
+++ b/src/Helpers/SAMLHelper.php
@@ -125,7 +125,7 @@ public function binToStrGuid($object_guid)
             $hex_guid_to_guid_str .= substr($hex_guid, 16 - 2 * $k, 2);
         }
         $hex_guid_to_guid_str .= '-' . substr($hex_guid, 16, 4);
-        $hex_guid_to_guid_str .= '-' . substr($hex_guid, 20);
+        $hex_guid_to_guid_str .= '-' . substr($hex_guid, 20, 12);
         return strtoupper($hex_guid_to_guid_str);
     }
 
diff --git a/tests/php/Helpers/SAMLHelperTest.php b/tests/php/Helpers/SAMLHelperTest.php
index fd793a3..14df03c 100644
--- a/tests/php/Helpers/SAMLHelperTest.php
+++ b/tests/php/Helpers/SAMLHelperTest.php
@@ -36,6 +36,6 @@ public function guidProvider()
     public function testBinToStrGuid()
     {
         $result = SAMLHelper::singleton()->binToStrGuid('thequ!ckbrownf0xjumpsov3rthel4zyd06');
-        $this->assertSame('71656874-2175-6B63-6272-6F776E6630786A756D70736F7633727468656C347A79643036', $result);
+        $this->assertSame('71656874-2175-6B63-6272-6F776E663078', $result);
     }
 }