Android : Android Build: Classes of a JAR file inside a AAR package are not recognized

I have a library project that I wan't to share as AAR file.

This library project contains several JAR files, some of them are classes I made and are used in the library project. For example I have a class in the lib project that inherits from a class inside the JAR file.

I was able to create the AAR file, and now I'm testing the AAR file in a sample app made in Android Studio.

I added the AAR file modifying the build.gradle file of the app module like this:

repositories {
    flatDir {
        dirs 'libs'
    }
}
dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile(name: 'mightylibrary', ext:'aar')
    compile 'com.android.support:appcompat-v7:20.+'
}

Then when I try to use methods from the parent class I'm not able to see them, only the methods implemented in the child class.

Is there any known limitation of accessing classes inside JARs packaged within a AAR file?

Any solution?

Thanks