Initial monitor does not output anything on Windows (MSYS2 binary)

When running on Windows error messages before the UI is started are not showing up.

For example when I run:

qemu-system-i386.exe -L /mingw32/etc/qemu/ -m 20G

It should display "ram size too large", according to gdb:

Breakpoint 1, error_report (fmt=fmt@entry=0x71bdf6 <dma_aiocb_info+2426> "ram size too large") at C:/build/mingw/mingw-w64-qemu/src/qemu-2.4.0/util/qemu-error.c:233

However the console does never receive that.

As far as I could find out vfprintf is called, but it doesn't output anything.