--- a/devtools/client/shared/test/test-actor-registry.js
+++ b/devtools/client/shared/test/test-actor-registry.js
@@ -77,16 +77,19 @@ exports.getTestActorWithoutToolbox = Tas
     DebuggerServer.addBrowserActors();
   }
   let client = new DebuggerClient(DebuggerServer.connectPipe());
 
   let deferred = promise.defer();
   client.connect(deferred.resolve);
   yield deferred.promise;
 
+  // We also need to make sure the test actor is registered on the server.
+  yield registerTestActor(client);
+
   return getTestActor(client, tab);
 });
 
 // Fetch the content of a URI
 var request = function (uri) {
   return fetch(uri).then(({ content }) => content);
 }