diff --git a/code/extensions/GroupSubsites.php b/code/extensions/GroupSubsites.php
index bd60f00a..a0290a2e 100644
--- a/code/extensions/GroupSubsites.php
+++ b/code/extensions/GroupSubsites.php
@@ -123,20 +123,20 @@ public function updateCMSFields(FieldList $fields)
     }
 
     /**
-     * If this group belongs to a subsite,
-     * append the subsites title to the group title
-     * to make it easy to distinguish in the tree-view
-     * of the security admin interface.
+     * If this group belongs to a subsite, append the subsites title to the group title to make it easy to
+     * distinguish in the tree-view of the security admin interface.
+     *
+     * @param string $title
      */
-    public function alternateTreeTitle()
+    public function updateTreeTitle(&$title)
     {
         if ($this->owner->AccessAllSubsites) {
             $title = _t('GroupSubsites.GlobalGroup', 'global group');
-            return htmlspecialchars($this->owner->Title, ENT_QUOTES) . ' <i>(' . $title . ')</i>';
+            $title = htmlspecialchars($this->owner->Title, ENT_QUOTES) . ' <i>(' . $title . ')</i>';
+        } else {
+            $subsites = Convert::raw2xml(implode(', ', $this->owner->Subsites()->column('Title')));
+            $title = htmlspecialchars($this->owner->Title) . " <i>($subsites)</i>";
         }
-
-        $subsites = Convert::raw2xml(implode(', ', $this->owner->Subsites()->column('Title')));
-        return htmlspecialchars($this->owner->Title) . " <i>($subsites)</i>";
     }
 
     /**
diff --git a/tests/php/GroupSubsitesTest.php b/tests/php/GroupSubsitesTest.php
index ed35292a..c2eaa3e4 100644
--- a/tests/php/GroupSubsitesTest.php
+++ b/tests/php/GroupSubsitesTest.php
@@ -15,8 +15,8 @@ class GroupSubsitesTest extends BaseSubsiteTest
 
     public function testTrivialFeatures()
     {
-        $this->assertTrue(is_array(singleton(GroupSubsites::class)->extraStatics()));
-        $this->assertTrue(is_array(singleton(GroupSubsites::class)->providePermissions()));
+        $this->assertInternalType('array', singleton(GroupSubsites::class)->extraStatics());
+        $this->assertInternalType('array', singleton(GroupSubsites::class)->providePermissions());
         $this->assertInstanceOf(FieldList::class, singleton(Group::class)->getCMSFields());
     }
 
@@ -25,11 +25,13 @@ public function testAlternateTreeTitle()
         $group = new Group();
         $group->Title = 'The A Team';
         $group->AccessAllSubsites = true;
-        $this->assertEquals($group->getTreeTitle(), 'The A Team <i>(global group)</i>');
+        $this->assertEquals('The A Team <i>(global group)</i>', $group->getTreeTitle());
+
         $group->AccessAllSubsites = false;
         $group->write();
+
         $group->Subsites()->add($this->objFromFixture(Subsite::class, 'domaintest1'));
         $group->Subsites()->add($this->objFromFixture(Subsite::class, 'domaintest2'));
-        $this->assertEquals($group->getTreeTitle(), 'The A Team <i>(Test 1, Test 2)</i>');
+        $this->assertEquals('The A Team <i>(Test 1, Test 2)</i>', $group->getTreeTitle());
     }
 }