diff --git a/CrossPlatformModules.csproj b/CrossPlatformModules.csproj
index 6f70de19b..474b27b98 100644
--- a/CrossPlatformModules.csproj
+++ b/CrossPlatformModules.csproj
@@ -3,7 +3,7 @@
   <PropertyGroup>
     <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">12.0</VisualStudioVersion>
     <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
-    <TypeScriptToolsVersion>1.5</TypeScriptToolsVersion>
+    <TypeScriptToolsVersion>1.6</TypeScriptToolsVersion>
     <ProjectGuid>{2313F1BF-1F2D-4F11-806A-87927FA6A7C0}</ProjectGuid>
     <ProjectTypeGuids>{349c5851-65df-11da-9384-00065b846f21};{fae04ec0-301f-11d3-bf4b-00c04f79efbc}</ProjectTypeGuids>
     <OutputType>Library</OutputType>
@@ -1977,7 +1977,7 @@
           <SaveServerSettingsInUserFile>False</SaveServerSettingsInUserFile>
         </WebProjectProperties>
       </FlavorProperties>
-      <UserProperties ui_2scroll-view_2package_1json__JSONSchema="http://json.schemastore.org/package" apps_2editable-text-demo_2package_1json__JSONSchema="http://json.schemastore.org/package" apps_2absolute-layout-demo_2package_1json__JSONSchema="http://json.schemastore.org/package" apps_2gallery-app_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2content-view_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2web-view_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2layouts_2absolute-layout_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2layouts_2dock-layout_2package_1json__JSONSchema="" ui_2layouts_2grid-layout_2package_1json__JSONSchema="" ui_2layouts_2wrap-layout_2package_1json__JSONSchema="http://json.schemastore.org/package" />
+      <UserProperties ui_2layouts_2wrap-layout_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2layouts_2grid-layout_2package_1json__JSONSchema="" ui_2layouts_2dock-layout_2package_1json__JSONSchema="" ui_2layouts_2absolute-layout_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2web-view_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2content-view_2package_1json__JSONSchema="http://json.schemastore.org/package" apps_2gallery-app_2package_1json__JSONSchema="http://json.schemastore.org/package" apps_2absolute-layout-demo_2package_1json__JSONSchema="http://json.schemastore.org/package" apps_2editable-text-demo_2package_1json__JSONSchema="http://json.schemastore.org/package" ui_2scroll-view_2package_1json__JSONSchema="http://json.schemastore.org/package" />
     </VisualStudio>
   </ProjectExtensions>
 </Project>
\ No newline at end of file
diff --git a/data/observable/observable.ts b/data/observable/observable.ts
index 9404e1f5c..3fd51a3c3 100644
--- a/data/observable/observable.ts
+++ b/data/observable/observable.ts
@@ -53,7 +53,12 @@ export class Observable implements definition.Observable {
     }
 
     public addEventListener(eventNames: string, callback: (data: definition.EventData) => void, thisArg?: any) {
+        if (!types.isString(eventNames)) {
+            throw new TypeError("Events name(s) must be string.");
+        }
+
         types.verifyCallback(callback);
+
         var events: Array<string> = eventNames.split(",");
 
         for (var i = 0, l = events.length; i < l; i++) {
@@ -68,6 +73,10 @@ export class Observable implements definition.Observable {
     }
 
     public removeEventListener(eventNames: string, callback?: any, thisArg?: any) {
+        if (!types.isString(eventNames)) {
+            throw new TypeError("Events name(s) must be string.");
+        }
+
         var events: Array<string> = eventNames.split(",");
 
         for (var i = 0, l = events.length; i < l; i++) {