Android light theme with action bar

I want to use a light theme, but still have an actionbar visible.

From here it looks like this should work:

<activity android:theme="@style/Theme.AppCompat.Light" ... >

But when I add any android:theme the actionbar disappears.

I'm probably missing something obvious...

Edit: in case it helps

From the build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.company.app"
        minSdkVersion 15
        targetSdkVersion 21
        versionCode 5
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.0.0'
}