Trying to use SmartGWT but getting errors: “Cannot

I am trying to introduce SmartGWT to my existing GWT application.

What I did so far was placing

<inherits name="com.smartgwt.SmartGwt"/>

into my client.gwt.xml and module.gwt.xml files. If I run the application, the compilation appears to work. I am not getting any errors from the code server - just a few warnings about deprecated classes but nothing else.

However, if I just import a SmartGWT button like this:

public LandingPageViewImpl() {
    initWidget(uiBinder.createAndBindUi(this));
    AppPlaceHistoryMapper historyMapper = Util.placeHistoryMapper;

    final LoginPlace loginPlace = new LoginPlace();
    this.aLogin.setHref("#" + historyMapper.getToken(loginPlace));

    // This is "com.smartgwt.client.widgets.Button"
    Button btn = new Button();
}

My application breaks and I am getting

Caused by: com.google.gwt.core.client.JavaScriptException: (TypeError) : Cannot read property 'setAutoDraw' of undefined

I am quite sure that I'm missing something but the question is what. I am using the latest SmartGWT version v5.0-p20160115

<dependency>
    <groupId>com.isomorphic.smartgwt.lgpl</groupId>
    <artifactId>smartgwt-lgpl</artifactId>
    <version>5.0-p20160115</version>
</dependency>

<!-- Required by Smart GWT -->
<dependency>
    <groupId>com.isomorphic</groupId>
    <artifactId>isc-maven-plugin</artifactId>
    <version>1.1.1</version>
</dependency>

after installing SmartGWT

mvn com.isomorphic:isc-maven-plugin:install -Dproduct=SMARTGWT -Dlicense=LGPL -DbuildNumber=5.0p

besides the latest GWT version v2.8.0-beta1

<dependency>
    <groupId>com.google.gwt</groupId>
    <artifactId>gwt</artifactId>
    <version>2.8.0-beta1</version>
    <type>pom</type>
    <scope>import</scope>
</dependency>