diff --git a/src/add-ons/kernel/drivers/ports/usb_serial/Driver.cpp b/src/add-ons/kernel/drivers/ports/usb_serial/Driver.cpp
index 77f9f74643..fb88813c9e 100644
--- a/src/add-ons/kernel/drivers/ports/usb_serial/Driver.cpp
+++ b/src/add-ons/kernel/drivers/ports/usb_serial/Driver.cpp
@@ -351,7 +351,7 @@ publish_devices()
 		if (gSerialDevices[i]) {
 			gDeviceNames[j] = (char *)malloc(strlen(sDeviceBaseName) + 4);
 			if (gDeviceNames[j]) {
-				sprintf(gDeviceNames[j], "%s%ld", sDeviceBaseName, i);
+				sprintf(gDeviceNames[j], "%s%" B_PRId32, sDeviceBaseName, i);
 				j++;
 			} else
 				TRACE_ALWAYS("publish_devices - no memory to allocate device names\n");
diff --git a/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.cpp b/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.cpp
index e8bb192c35..4af8c16a30 100644
--- a/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.cpp
+++ b/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.cpp
@@ -669,7 +669,7 @@ SerialDevice::_WriteToDevice()
 
 void
 SerialDevice::_ReadCallbackFunction(void *cookie, status_t status, void *data,
-	uint32 actualLength)
+	size_t actualLength)
 {
 	TRACE_FUNCALLS("read callback: cookie: 0x%08x status: 0x%08x data: 0x%08x "
 		"length: %lu\n", cookie, status, data, actualLength);
@@ -683,7 +683,7 @@ SerialDevice::_ReadCallbackFunction(void *cookie, status_t status, void *data,
 
 void
 SerialDevice::_WriteCallbackFunction(void *cookie, status_t status, void *data,
-	uint32 actualLength)
+	size_t actualLength)
 {
 	TRACE_FUNCALLS("write callback: cookie: 0x%08x status: 0x%08x data: 0x%08x "
 		"length: %lu\n", cookie, status, data, actualLength);
@@ -697,7 +697,7 @@ SerialDevice::_WriteCallbackFunction(void *cookie, status_t status, void *data,
 
 void
 SerialDevice::_InterruptCallbackFunction(void *cookie, status_t status,
-	void *data, uint32 actualLength)
+	void *data, size_t actualLength)
 {
 	TRACE_FUNCALLS("interrupt callback: cookie: 0x%08x status: 0x%08x data: "
 		"0x%08x len: %lu\n", cookie, status, data, actualLength);
diff --git a/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.h b/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.h
index 57afc10cb7..213e2556d8 100644
--- a/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.h
+++ b/src/add-ons/kernel/drivers/ports/usb_serial/SerialDevice.h
@@ -95,13 +95,13 @@ static	int32					_InputThread(void *data);
 
 static	void					_ReadCallbackFunction(void *cookie,
 									int32 status, void *data,
-									uint32 actualLength);
+									size_t actualLength);
 static	void					_WriteCallbackFunction(void *cookie,
 									int32 status, void *data,
-									uint32 actualLength);
+									size_t actualLength);
 static	void					_InterruptCallbackFunction(void *cookie,
 									int32 status, void *data,
-									uint32 actualLength);
+									size_t actualLength);
 
 		usb_device				fDevice;		// USB device handle
 		uint16					fVendorID;