Golang类型断言失败

In Golang, I am trying to convert an Interface to Slice of Bytes. Debugger clearly shows that it is a Slice of Bytes.

    // Check an Interface's Type.
    ifcType = reflect.TypeOf(ifc).Kind()

    // Array?
    if ifcType == reflect.Slice {

        // Get Type of Sub-Elements.
        ifcElementType = reflect.TypeOf(ifc).Elem().Kind()
        if ifcElementType == reflect.Uint8 {

            // Array of Bytes.
            // => 'bencode' Byte String.

            // Convert the Type.
            ba, ok = ifc.([]byte)
            if !ok {
                return nil, ErrTypeAssertion
            }

When I have checked that Interface's Type is Slice and Sub-Item's Type is Uint8, I do the Type Assertion. But for some Reason, it fails. How can that be ?

GoLand's Debugger Screenshot just after 'ok' Variable has become 'false': http://imagehost.cc/image/v4403

Thank you!