Error with associative array initializer DMD32 D Compiler v2.070.0

[MGW via Digitalmars-d-learn]

immutable long[string] aa = [
    "foo": 5,
    "bar": 10,
    "baz": 2000
];

... Error: non-constant expression ["foo":5L, "bar":10L, 
"baz":2000L]