diff --git a/package.json b/package.json
index d83a8a1066..dc692706b9 100644
--- a/package.json
+++ b/package.json
@@ -183,7 +183,7 @@
     "sinon-chai": "^2.8.0",
     "source-map-support": "^0.4.0",
     "tslint": "^3.15.1",
-    "typescript": "^1.8.10",
+    "typescript": "^2.0.3",
     "typings": "^1.3.3",
     "validate-commit-msg": "^2.3.1",
     "watch": "^0.18.0",
diff --git a/spec/subjects/BehaviorSubject-spec.ts b/spec/subjects/BehaviorSubject-spec.ts
index 2b1c602836..89050ab9d9 100644
--- a/spec/subjects/BehaviorSubject-spec.ts
+++ b/spec/subjects/BehaviorSubject-spec.ts
@@ -44,7 +44,8 @@ describe('BehaviorSubject', () => {
     const subject = new BehaviorSubject('flibberty');
 
     try {
-      subject.value = 'jibbets';
+      // XXX: escape from readonly restriction for testing.
+      (subject as any).value = 'jibbets';
     } catch (e) {
       //noop
     }