diff --git a/reactos/drivers/bus/serenum/detect.c b/reactos/drivers/bus/serenum/detect.c
index c1c7680c5f0..5cf8cc033d5 100644
--- a/reactos/drivers/bus/serenum/detect.c
+++ b/reactos/drivers/bus/serenum/detect.c
@@ -338,7 +338,7 @@ SerenumDetectPnpDevice(
 	if (!NT_SUCCESS(Status)) goto ByeBye;
 	Purge = SERIAL_PURGE_RXABORT | SERIAL_PURGE_RXCLEAR;
 	Status = DeviceIoControl(LowerDevice, IOCTL_SERIAL_PURGE,
-		&Purge, 0, NULL, NULL);
+		&Purge, sizeof(ULONG), NULL, NULL);
 	if (!NT_SUCCESS(Status)) goto ByeBye;
 	Wait(200);