diff --git a/Libraries/LibWeb/HTML/MessagePort.cpp b/Libraries/LibWeb/HTML/MessagePort.cpp
index b347fe554be..2c955155490 100644
--- a/Libraries/LibWeb/HTML/MessagePort.cpp
+++ b/Libraries/LibWeb/HTML/MessagePort.cpp
@@ -99,7 +99,11 @@ WebIDL::ExceptionOr<void> MessagePort::transfer_steps(HTML::TransferDataEncoder&
     // 3. If value is entangled with another port remotePort, then:
     if (is_entangled()) {
         // 1. Set remotePort's has been shipped flag to true.
-        m_remote_port->m_has_been_shipped = true;
+
+        // NOTE: We have to null check here because we can be entangled with a port living in another agent.
+        //       In that case, we'll have a transport, but no remote port object.
+        if (m_remote_port)
+            m_remote_port->m_has_been_shipped = true;
 
         auto fd = MUST(m_transport->release_underlying_transport_for_transfer());
         m_transport.clear();
diff --git a/Tests/LibWeb/Text/expected/HTML/MessagePort-transfer-twice.txt b/Tests/LibWeb/Text/expected/HTML/MessagePort-transfer-twice.txt
new file mode 100644
index 00000000000..33c112e2685
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/HTML/MessagePort-transfer-twice.txt
@@ -0,0 +1,2 @@
+first receipt: re-transferring same port
+we good
diff --git a/Tests/LibWeb/Text/input/HTML/MessagePort-transfer-twice.html b/Tests/LibWeb/Text/input/HTML/MessagePort-transfer-twice.html
new file mode 100644
index 00000000000..d0245d81383
--- /dev/null
+++ b/Tests/LibWeb/Text/input/HTML/MessagePort-transfer-twice.html
@@ -0,0 +1,27 @@
+<!doctype html>
+<script src="../include.js"></script>
+<script>
+    asyncTest(done => {
+        function onFirst(e) {
+            const port = (e.data && e.data.port) || (e.ports && e.ports[0]);
+            if (!port) return;
+
+            println("first receipt: re-transferring same port");
+            window.removeEventListener("message", onFirst);
+            window.addEventListener("message", onSecond);
+            window.postMessage({ port }, "*", [port]);
+        }
+
+        function onSecond(e) {
+            println("we good");
+            done();
+        }
+
+        window.addEventListener("message", onFirst);
+
+        const { port1, port2 } = new MessageChannel();
+        port1.onmessage = e => println("main saw: " + e.data);
+
+        window.postMessage({ port: port2 }, "*", [port2]);
+    });
+</script>
