Cannot get thread ID with Thread.getThis() in specific callback functions on Windows

[Haruki Shigemori]

Hi.
I cannot get thread ID with Thread.getThis() in specific callback
functions on Windows.
What is the cause of this problem?

import win32.windows;
import win32.mmsystem;
import std.stdio;
import core.thread;

extern (Windows)
void waveInProc(in HWAVEIN handle, in uint message, in DWORD instance,
in DWORD param1, in DWORD param2)
{
        auto tid = Thread.getThis();
        assert(tid); // tid is null
}

void main()
{
        WAVEFORMATEX formatEx;
        with (formatEx)
        {
                wFormatTag = WAVE_FORMAT_PCM;
                nChannels = 1;
                nSamplesPerSec = 44100;
                wBitsPerSample = 16;
                nBlockAlign = cast(ushort)(wBitsPerSample * nChannels / 8);
                nAvgBytesPerSec = nSamplesPerSec * nBlockAlign;
        }

        HWAVEIN handle;
        waveInOpen(&handle, WAVE_MAPPER, cast(WAVEFORMATEX*)&formatEx,
cast(DWORD)&waveInProc, cast(DWORD)null, CALLBACK_FUNCTION);

        uint bufferSize = cast(uint)(formatEx.nAvgBytesPerSec *
1/+second+/);
        WAVEHDR* hdr = new WAVEHDR;
        hdr.lpData = cast(LPSTR)new ushort[bufferSize];
        hdr.dwBufferLength = bufferSize;
        hdr.dwFlags = 0;
        hdr.dwLoops = 0;

        waveInPrepareHeader(handle, hdr, WAVEHDR.sizeof);
        waveInAddBuffer(handle, hdr, WAVEHDR.sizeof);
        waveInStart(handle);

        readln();
}