diff --git a/reactos/drivers/input/sermouse/detect.c b/reactos/drivers/input/sermouse/detect.c
index da5c333d84c..59ade5a3c63 100644
--- a/reactos/drivers/input/sermouse/detect.c
+++ b/reactos/drivers/input/sermouse/detect.c
@@ -20,9 +20,9 @@ DeviceIoControl(
 	IN PDEVICE_OBJECT DeviceObject,
 	IN ULONG CtlCode,
 	IN PVOID InputBuffer OPTIONAL,
-	IN ULONG InputBufferSize,
+	IN ULONG_PTR InputBufferSize,
 	IN OUT PVOID OutputBuffer OPTIONAL,
-	IN OUT PULONG OutputBufferSize)
+	IN OUT PULONG_PTR OutputBufferSize)
 {
 	KEVENT Event;
 	PIRP Irp;
@@ -106,7 +106,7 @@ ReadBytes(
 	IN PDEVICE_OBJECT LowerDevice,
 	OUT PUCHAR Buffer,
 	IN ULONG BufferSize,
-	OUT PULONG FilledBytes)
+	OUT PULONG_PTR FilledBytes)
 {
 	PIRP Irp;
 	IO_STATUS_BLOCK ioStatus;
@@ -160,7 +160,7 @@ SermouseDetectLegacyDevice(
 	ULONG Command;
 	SERIAL_TIMEOUTS Timeouts;
 	SERIAL_LINE_CONTROL LCR;
-	ULONG i, Count = 0;
+	ULONG_PTR i, Count = 0;
 	UCHAR Buffer[16];
 	SERMOUSE_MOUSE_TYPE MouseType = mtNone;
 	NTSTATUS Status;
diff --git a/reactos/drivers/input/sermouse/fdo.c b/reactos/drivers/input/sermouse/fdo.c
index c3e5b0f1c5d..c62b649d5c2 100644
--- a/reactos/drivers/input/sermouse/fdo.c
+++ b/reactos/drivers/input/sermouse/fdo.c
@@ -139,7 +139,7 @@ SermousePnp(
 {
 	ULONG MinorFunction;
 	PIO_STACK_LOCATION Stack;
-	ULONG Information = 0;
+	ULONG_PTR Information = 0;
 	NTSTATUS Status;
 
 	Stack = IoGetCurrentIrpStackLocation(Irp);
diff --git a/reactos/drivers/input/sermouse/sermouse.h b/reactos/drivers/input/sermouse/sermouse.h
index e7af934acc7..fa2b3163456 100644
--- a/reactos/drivers/input/sermouse/sermouse.h
+++ b/reactos/drivers/input/sermouse/sermouse.h
@@ -54,7 +54,7 @@ typedef enum
 
 typedef struct _SERMOUSE_DRIVER_EXTENSION
 {
-	ULONG NumberOfButtons;
+	USHORT NumberOfButtons;
 } SERMOUSE_DRIVER_EXTENSION, *PSERMOUSE_DRIVER_EXTENSION;
 
 typedef struct _SERMOUSE_DEVICE_EXTENSION