Specifying TestList while using MSTest

I'm setting up TeamCity for our project, and I've ran into an issue when specifying Testlists under MSTest

The field "Testlist from metadata to run" should allow multiple items to be entered, where each item is turned into a /testlist:FooList. However, when I set it to

Foo

Bar

The test runner calls

MSTest <snip> /testlist:Foo

Bar

instead of the expected

MSTest <snip> /testlist:Foo /testlist:Bar

I'm using TC 5.1.1 on Windows.

What am I doing wrong?

TIA