Dub subpackage woes

app1.d

module app1;

import std.stdio;

import lib1;

void main() {
    add(2,3).println;
}

lib1.d

module lib1;

int add(int x, int y) {
    return x - y;
}

package.json

{
    "name": "testpkg",
    "targetType": "none",
    "version": "~master",
    "description": "An example project skeleton",
    "homepage": "http://example.org",
    "copyright": "Copyright © 2000, Your Name",
    "authors": [
        "Your Name"
    ],

    "dependencies": {
        "testpkg:lib1": "~master",
        "testpkg:app1": "~master"
    },

    "targetPath": "lib",
    "importPaths": ["import"],

    "subPackages": [
    {
        "name":"lib1",
        "version": "~master",
        "targetType": "library",
        "targetName": "lib1",
        "targetPath": "lib",
        "importPaths": ["import"],
        "sourcePaths": ["import/lib1"]
    },
    {
        "name":"app1",
        "version": "~master",
        "targetType": "executable",
        "targetName": "app1",
        "targetPath": "bin",
        "importPaths": ["import"],
        "sourcePaths": ["import/app1"],
        "dependencies": {"testpkg:lib1": "~master"}
    }
    ],
}