GLSL compiler error: type mismatch for mix as select

Driver Packaging Version: 14.10.1006-140417a-171099C

Catalyst Version: 14.4

Code:

uvec4 func( )

{

    return mix( uvec4(0), uvec4(1), bvec4(true) ) ;

}

Error:

error(#247) Function return does not match type

But OpenGL QuickRef. Guide says:

T mix( T x, T y, bvec )

So whats the matter? What does mix return in the code example?

Thanks,

Alex