diff --git a/src/Core/Manifest/ClassManifest.php b/src/Core/Manifest/ClassManifest.php
index 9d406620d..0e2887635 100644
--- a/src/Core/Manifest/ClassManifest.php
+++ b/src/Core/Manifest/ClassManifest.php
@@ -650,6 +650,11 @@ class ClassManifest
                     }
                     $this->children[$lowerAncestor][$lowerClassName] = $className;
                 }
+
+                // If the class extends a core class, add class to roots
+                if (strpos($ancestor, 'SilverStripe\\Control') === 0) {
+                    $this->roots[$lowerAncestor] = $ancestor;
+                }
             } else {
                 $this->roots[$lowerClassName] = $className;
             }
diff --git a/tests/php/Core/ClassInfoTest.php b/tests/php/Core/ClassInfoTest.php
index a1d353483..7528c3f36 100644
--- a/tests/php/Core/ClassInfoTest.php
+++ b/tests/php/Core/ClassInfoTest.php
@@ -87,6 +87,14 @@ class ClassInfoTest extends SapphireTest
             $subclassesWithoutBase,
             ClassInfo::subclassesFor('silverstripe\\core\\tests\\classinfotest\\baseclass', false)
         );
+
+        // Check that core classes are present (eg: Email subclasses)
+        $emailClasses = ClassInfo::subclassesFor(\SilverStripe\Control\Email\Email::class);
+        $this->assertArrayHasKey(
+            'silverstripe\\control\\tests\\email\\emailtest\\emailsubclass',
+            $emailClasses,
+            'It contains : ' . json_encode($emailClasses)
+        );
     }
 
     public function testClassName()