Assertion 'Irp->Type == IO_TYPE_IRP' failed at ntoskrnl/io/iomgr/irp.c line 991

In r48414, happening randomly in 2nd stage. VBox, AMD-v and NP enabled, 256MB ram

Assertion 'Irp->Type == IO_TYPE_IRP' failed at ntoskrnl/io/iomgr/irp.c line 991
Entered debugger on embedded INT3 at 0x0008:0x808ed12e.
kdb:> bt
Eip:
<ntoskrnl.exe:ed12f (lib/rtl/i386/debug_asm.S:33 (DbgBreakPoint@0))>
Frames:
<ntoskrnl.exe:684b4 (ntoskrnl/io/iomgr/irp.c:991 (IoCancelIrp@4))>
<ntoskrnl.exe:697e9 (ntoskrnl/io/iomgr/irp.c:1054 (IoCancelThreadIo@4))>
<ntoskrnl.exe:d1474 (ntoskrnl/ps/kill.c:711 (PspExitThread@4))>
<ntoskrnl.exe:d18be (ntoskrnl/ps/kill.c:967 (PspTerminateThreadByPointer@12))>
<ntoskrnl.exe:d1a3b (ntoskrnl/ps/kill.c:1248 (NtTerminateThread@8))>
<ntoskrnl.exe:6d8e (ntoskrnl/ke/i386/traphdlr.c:1565 (@KiFastCallEntryHandler@8))>
<ntoskrnl.exe:e7731 (ntoskrnl/ke/i386/trap.s:133 (KiFastCallEntry))>
<ntdll.dll:7ac9>
<kernel32.dll:33539>
<00000000>
kdb:>