diff --git a/components/script/dom/extendablemessageevent.rs b/components/script/dom/extendablemessageevent.rs
index dab06b7d79db..6131363fd99e 100644
--- a/components/script/dom/extendablemessageevent.rs
+++ b/components/script/dom/extendablemessageevent.rs
@@ -7,7 +7,7 @@ use crate::dom::bindings::codegen::Bindings::ExtendableMessageEventBinding::Exte
 use crate::dom::bindings::error::Fallible;
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::reflector::reflect_dom_object;
-use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::bindings::trace::RootedTraceableBox;
 use crate::dom::bindings::utils::message_ports_to_frozen_array;
@@ -31,10 +31,27 @@ pub struct ExtendableMessageEvent {
     data: Heap<JSVal>,
     origin: DOMString,
     lastEventId: DOMString,
-    ports: Vec<DomRoot<MessagePort>>,
+    ports: Vec<Dom<MessagePort>>,
 }
 
 impl ExtendableMessageEvent {
+    pub fn new_inherited(
+        origin: DOMString,
+        lastEventId: DOMString,
+        ports: Vec<DomRoot<MessagePort>>,
+    ) -> ExtendableMessageEvent {
+        ExtendableMessageEvent {
+            event: ExtendableEvent::new_inherited(),
+            data: Heap::default(),
+            origin: origin,
+            lastEventId: lastEventId,
+            ports: ports
+                .into_iter()
+                .map(|port| Dom::from_ref(&*port))
+                .collect(),
+        }
+    }
+
     pub fn new(
         global: &GlobalScope,
         type_: Atom,
@@ -45,13 +62,11 @@ impl ExtendableMessageEvent {
         lastEventId: DOMString,
         ports: Vec<DomRoot<MessagePort>>,
     ) -> DomRoot<ExtendableMessageEvent> {
-        let ev = Box::new(ExtendableMessageEvent {
-            event: ExtendableEvent::new_inherited(),
-            data: Heap::default(),
+        let ev = Box::new(ExtendableMessageEvent::new_inherited(
             origin,
             lastEventId,
             ports,
-        });
+        ));
         let ev = reflect_dom_object(ev, global, ExtendableMessageEventBinding::Wrap);
         {
             let event = ev.upcast::<Event>();
@@ -126,6 +141,11 @@ impl ExtendableMessageEventMethods for ExtendableMessageEvent {
 
     /// https://w3c.github.io/ServiceWorker/#extendablemessage-event-ports
     fn Ports(&self, cx: JSContext) -> JSVal {
-        message_ports_to_frozen_array(self.ports.as_slice(), cx)
+        let ports: Vec<DomRoot<MessagePort>> = self
+            .ports
+            .iter()
+            .map(|port| DomRoot::from_ref(&**port))
+            .collect();
+        message_ports_to_frozen_array(ports.as_slice(), cx)
     }
 }
diff --git a/components/script/dom/messageevent.rs b/components/script/dom/messageevent.rs
index cc5725ffb6c6..0bb2ea1fd7a9 100644
--- a/components/script/dom/messageevent.rs
+++ b/components/script/dom/messageevent.rs
@@ -60,10 +60,31 @@ pub struct MessageEvent {
     origin: DomRefCell<DOMString>,
     source: DomRefCell<Option<SrcObject>>,
     lastEventId: DomRefCell<DOMString>,
-    ports: DomRefCell<Vec<DomRoot<MessagePort>>>,
+    ports: DomRefCell<Vec<Dom<MessagePort>>>,
 }
 
 impl MessageEvent {
+    pub fn new_inherited(
+        origin: DOMString,
+        source: Option<&WindowProxyOrMessagePortOrServiceWorker>,
+        lastEventId: DOMString,
+        ports: Vec<DomRoot<MessagePort>>,
+    ) -> MessageEvent {
+        MessageEvent {
+            event: Event::new_inherited(),
+            data: Heap::default(),
+            source: DomRefCell::new(source.map(|source| source.into())),
+            origin: DomRefCell::new(origin),
+            lastEventId: DomRefCell::new(lastEventId),
+            ports: DomRefCell::new(
+                ports
+                    .into_iter()
+                    .map(|port| Dom::from_ref(&*port))
+                    .collect(),
+            ),
+        }
+    }
+
     pub fn new_uninitialized(global: &GlobalScope) -> DomRoot<MessageEvent> {
         MessageEvent::new_initialized(
             global,
@@ -83,14 +104,12 @@ impl MessageEvent {
         lastEventId: DOMString,
         ports: Vec<DomRoot<MessagePort>>,
     ) -> DomRoot<MessageEvent> {
-        let ev = Box::new(MessageEvent {
-            event: Event::new_inherited(),
-            data: Heap::default(),
-            source: DomRefCell::new(source.map(|source| source.into())),
-            origin: DomRefCell::new(origin),
-            lastEventId: DomRefCell::new(lastEventId),
-            ports: DomRefCell::new(ports),
-        });
+        let ev = Box::new(MessageEvent::new_inherited(
+            origin,
+            source,
+            lastEventId,
+            ports,
+        ));
         let ev = reflect_dom_object(ev, global, MessageEventBinding::Wrap);
         ev.data.set(data.get());
 
@@ -219,7 +238,13 @@ impl MessageEventMethods for MessageEvent {
 
     /// <https://html.spec.whatwg.org/multipage/#dom-messageevent-ports>
     fn Ports(&self, cx: JSContext) -> JSVal {
-        message_ports_to_frozen_array(self.ports.borrow().as_slice(), cx)
+        let ports: Vec<DomRoot<MessagePort>> = self
+            .ports
+            .borrow()
+            .iter()
+            .map(|port| DomRoot::from_ref(&**port))
+            .collect();
+        message_ports_to_frozen_array(ports.as_slice(), cx)
     }
 
     /// <https://html.spec.whatwg.org/multipage/#dom-messageevent-initmessageevent>
@@ -239,7 +264,10 @@ impl MessageEventMethods for MessageEvent {
         *self.origin.borrow_mut() = origin.clone();
         *self.source.borrow_mut() = source.as_ref().map(|source| source.into());
         *self.lastEventId.borrow_mut() = lastEventId.clone();
-        *self.ports.borrow_mut() = ports;
+        *self.ports.borrow_mut() = ports
+            .into_iter()
+            .map(|port| Dom::from_ref(&*port))
+            .collect();
         self.event
             .init_event(Atom::from(type_), bubbles, cancelable);
     }