diff --git a/common/predictive-text/unit_tests/headless/worker-predict-dummy.js b/common/predictive-text/unit_tests/headless/worker-predict-dummy.js
index 04d0b2e545..3d05ceea8d 100644
--- a/common/predictive-text/unit_tests/headless/worker-predict-dummy.js
+++ b/common/predictive-text/unit_tests/headless/worker-predict-dummy.js
@@ -8,8 +8,10 @@ var sinon = require('sinon');
 var DummyModel = require('../../build/intermediate').models.DummyModel;
 
 describe('LMLayerWorker dummy model', function() {
-  it('can be instantiated with no arguments', function () {
-    var model = new DummyModel;
+  it('can be instantiated with capabilities', function () {
+    var model = new DummyModel({
+      maxLeftContextCodeUnits: 64,
+    });
     assert.isObject(model);
   });
 });
diff --git a/common/predictive-text/worker/dummy-model.ts b/common/predictive-text/worker/dummy-model.ts
index 4a14130324..d89620edf1 100644
--- a/common/predictive-text/worker/dummy-model.ts
+++ b/common/predictive-text/worker/dummy-model.ts
@@ -33,6 +33,6 @@
  * The Dummy Model that returns nonsensical, but predictable results. 
  */
 LMLayerWorker.models.DummyModel = class DummyModel implements WorkerInternalModel {
-  constructor() {
+  constructor(capabilities: Capabilities) {
   }
 };
diff --git a/common/predictive-text/worker/worker-interfaces.ts b/common/predictive-text/worker/worker-interfaces.ts
index c09aaeac8f..2181beaaea 100644
--- a/common/predictive-text/worker/worker-interfaces.ts
+++ b/common/predictive-text/worker/worker-interfaces.ts
@@ -73,6 +73,9 @@ interface WorkerInternalModel {
  * Constructors that return worker internal models.
  */
 interface WorkerInternalModelConstructor {
-  // TODO: new should take (cap: Capabilities)
-  new(): WorkerInternalModel;
+  /**
+   * WorkerInternalModel instances are all given the keyboard's
+   * capabilities.
+   */
+  new(capabilities: Capabilities): WorkerInternalModel;
 }