java.lang.IllegalArgumentException in RestServiceFactory

[safarious]

I'd like to use this library but got some troubles instantiating the API-Service. I tried debugging it but without success.

This is the code of my RestService:

@RestService
public interface ServiceApi {

@GET("/assignments/{id}")
@Cached(policy = CachePolicy.LOAD_IF_OFFLINE, timeToLive = 10 * 60 * 1000)
Assignment assignment(@Path("id") int assignmentId);

}

This is the code of my Activity:

public class restlessActivity extends Activity {

private String baseUrl =  "*URL*";
private ServiceApi mServiceApi;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_restless);

    RestClient mClient = RestClientFactory.defaultClient(getApplicationContext());
    mServiceApi = RestServiceFactory.getService(baseUrl, ServiceApi.class, mClient);
}

}

Logcat-Log:

 Caused by: java.lang.IllegalArgumentException
        at ly.apps.android.rest.utils.Types.getSupertype(Types.java:180)
        at ly.apps.android.rest.utils.ResponseTypeUtil.parseResponseType(ResponseTypeUtil.java:55)
        at ly.apps.android.rest.client.RestMethodCache.parseMethod(RestMethodCache.java:109)
        at ly.apps.android.rest.client.RestMethodCache.<init>(RestMethodCache.java:54)
        at ly.apps.android.rest.client.RestServiceFactory.initializeMethodCaches(RestServiceFactory.java:77)
        at ly.apps.android.rest.client.RestServiceFactory.getService(RestServiceFactory.java:57)
        at swisscom.restless.restlessActivity.onCreate(restlessActivity.java:24)
        at android.app.Activity.performCreate(Activity.java:5231)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2169)

            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)

I'm using Android 4.4.4 on my phone. I tested library version 1.2 and 1.2.1, dosen't work on both. Could you please let me know how I can fix this? @raulraja