.indexOf method(in javascript) returns wrong result when called with keyword array

The following expression should return "1":

(.indexOf (to-array [:a :b :c]) :b)

but actually the result is -1.
Note that this method call behaves normally with other type of array:

>(.indexOf (to-array ["a" "b" "c"]) "b")
>1

So I guess there might something wrong with the type Keyword.
Anyone have a look at this?