Signing product flavors with gradle

I am tyring to migrate my projects to gradle. One of my projects has multiple product flavors and each one of them has to be signed with a different signingConfig in its release version. So this is what I tried so far:

buildscript {
    ...
}

apply plugin: 'android'

android {
    compileSdkVersion 17
    buildToolsVersion '17'

    signingConfigs {
        flavor1 {
            storeFile file("keystore")
            storePassword "secret"
            keyAlias "aliasForFlavor1"
            keyPassword "secretFlavor1"
        }

        flavor2 {
            storeFile file("keystore")
            storePassword "secret"
            keyAlias "aliasForFlavor2"
            keyPassword "secretFlavor2"
        }
    }

    productFlavors {
        flavor1 {
            signingConfig signingConfigs.flavor1
        }

        flavor1 {
            signingConfig signingConfigs.flavor2
        }
    }
}

dependencies {
    ...
}

When I run gradle build I get a groovy.lang.MissingFieldException and the following error message:

No such field: signingConfigs for class: com.android.build.gradle.internal.dsl.GroupableProductFlavorFactory

So I assume the productFlavors.* part of the Gradle script is not the right place to put code signing configurations.

Per the user guide, signingConfigs for flavors are supported.

The problem here has to do with the scope of the signingConfigs object. I just assigned it to a variable inside the productFlavors block, but outside the flavor1 flavor block to fix the issue:

productFlavors {
    def flavor1SigningVariable = signingConfigs.flavor1

    flavor1 {
        ...
        signingConfig flavor1SigningVariable
        ...
    }