diff --git a/src/sys/iop.c b/src/sys/iop.c
index e953bb82..f34250ae 100644
--- a/src/sys/iop.c
+++ b/src/sys/iop.c
@@ -65,6 +65,7 @@ VOID FspIopCompleteRequestEx(PIRP Irp, NTSTATUS Result, BOOLEAN DeviceRelease)
     // !PAGED_CODE();
 
     ASSERT(STATUS_PENDING != Result);
+    ASSERT(0 == Irp->Tail.Overlay.DriverContext[3]);
 
     if (0 != Irp->Tail.Overlay.DriverContext[0])
     {