diff --git a/dom/base/CustomElementRegistry.cpp b/dom/base/CustomElementRegistry.cpp
index 59e107b14b..830f06fedf 100644
--- a/dom/base/CustomElementRegistry.cpp
+++ b/dom/base/CustomElementRegistry.cpp
@@ -523,9 +523,7 @@ static const char* kLifeCycleCallbackNames[] = {
   "adoptedCallback",
   "attributeChangedCallback",
   // The life cycle callbacks from v0 spec.
-  "createdCallback",
-  "attachedCallback",
-  "detachedCallback"
+  "createdCallback"
 };
 
 static void
diff --git a/dom/tests/mochitest/webcomponents/test_custom_element_register_invalid_callbacks.html b/dom/tests/mochitest/webcomponents/test_custom_element_register_invalid_callbacks.html
index a349f4aa50..d1b1b1e04c 100644
--- a/dom/tests/mochitest/webcomponents/test_custom_element_register_invalid_callbacks.html
+++ b/dom/tests/mochitest/webcomponents/test_custom_element_register_invalid_callbacks.html
@@ -20,8 +20,6 @@ const testWindow = iframe.contentDocument.defaultView;
 // We should do the same checks for the callbacks from v0 spec.
 [
   'createdCallback',
-  'attachedCallback',
-  'detachedCallback',
   'attributeChangedCallback',
 ].forEach(callback => {
   var c = class {};