Changed behaviour in TS2.1 for Promise<void>

In typescript 2.0 any promise could be used a promise of type void, this does not seem to be the case in typescript 2.1.

I couldn't find this listed as a breaking change or any existing tickets so raised this one.

TypeScript Version: 2.1.4

Code

function testVoidPromises(promiseA: Promise<void>, promiseB: Promise<void>): Promise<void> {
	return Promise.all([promiseA, promiseB]);
}

Expected behavior:
This compiles without errors in typescript 2.0

Actual behavior:
This fails to compile in typescript 2.1.4 with the following error:
test.ts(2,9): error TS2322: Type 'Promise<[void, void]>' is not assignable to type 'Promise'.
Type '[void, void]' is not assignable to type 'void'.

Start by compiling the provided test.ts example with TypeScript 2.1.4 and compare it with TypeScript 2.0, focusing on Promise.all's inferred return type. Trace the Promise.all type definitions or checker behavior involved; done means the expected Promise compatibility is restored or the changed behavior is documented with an appropriate regression test.