diff --git a/lib/questionlib.php b/lib/questionlib.php
index 99a7a2ce6b5..89c274e95cf 100644
--- a/lib/questionlib.php
+++ b/lib/questionlib.php
@@ -1434,7 +1434,7 @@ function question_has_capability_on($questionorid, $cap, $notused = -1): bool {
     } else if (is_object($questionorid)) {
         // All we really need in this function is the contextid and author of the question.
         // We won't bother fetching other details of the question if these 2 fields are provided.
-        if (isset($questionorid->contextid) && isset($questionorid->createdby)) {
+        if (isset($questionorid->contextid) && property_exists($questionorid, 'createdby')) {
             $question = $questionorid;
         } else if (!empty($questionorid->id)) {
             $questionid = $questionorid->id;
diff --git a/lib/tests/questionlib_test.php b/lib/tests/questionlib_test.php
index a84d41fe126..3102f5c149e 100644
--- a/lib/tests/questionlib_test.php
+++ b/lib/tests/questionlib_test.php
@@ -2024,6 +2024,35 @@ class questionlib_test extends \advanced_testcase {
         }
     }
 
+    /**
+     * Test that question_has_capability_on does not fail when passed an object with a null
+     * createdby property.
+     */
+    public function test_question_has_capability_on_object_with_null_createdby(): void {
+        $this->resetAfterTest();
+        $generator = $this->getDataGenerator();
+        $user = $generator->create_user();
+        $category = $generator->create_category();
+        $context = \context_coursecat::instance($category->id);
+
+        $role = $generator->create_role();
+        role_assign($role, $user->id, $context->id);
+        assign_capability('moodle/question:editmine', CAP_ALLOW, $role, $context->id);
+
+        $this->setUser($user);
+
+        $fakequestion = (object) [
+            'contextid' => $context->id,
+            'createdby' => null,
+        ];
+
+        $this->assertFalse(question_has_capability_on($fakequestion, 'edit'));
+
+        $fakequestion->createdby = $user->id;
+
+        $this->assertTrue(question_has_capability_on($fakequestion, 'edit'));
+    }
+
     /**
      * Test of question_categorylist function.
      *