diff --git a/rostests/kmtests/ntos_io/IoReadWrite_drv.c b/rostests/kmtests/ntos_io/IoReadWrite_drv.c
index 9a7679f0131..0c030685005 100644
--- a/rostests/kmtests/ntos_io/IoReadWrite_drv.c
+++ b/rostests/kmtests/ntos_io/IoReadWrite_drv.c
@@ -200,6 +200,7 @@ TestFastIoWrite(
     _Out_ PIO_STATUS_BLOCK IoStatus,
     _In_ PDEVICE_OBJECT DeviceObject)
 {
+    TestLastFastWriteKey = LockKey;
     UNIMPLEMENTED;
     return FALSE;
 }