diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index 7a5fa3770e..77ce89d38b 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -204,7 +204,7 @@ static void usb_serial_reset(USBSerialState *s)
 
 static void usb_serial_handle_reset(USBDevice *dev)
 {
-    USBSerialState *s = (USBSerialState *)dev;
+    USBSerialState *s = USB_SERIAL(dev);
 
     DPRINTF("Reset\n");
 
@@ -243,7 +243,7 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p,
                                       int request, int value, int index,
                                       int length, uint8_t *data)
 {
-    USBSerialState *s = (USBSerialState *)dev;
+    USBSerialState *s = USB_SERIAL(dev);
     int ret;
 
     DPRINTF("got control %x, value %x\n", request, value);
@@ -430,7 +430,7 @@ static void usb_serial_token_in(USBSerialState *s, USBPacket *p)
 
 static void usb_serial_handle_data(USBDevice *dev, USBPacket *p)
 {
-    USBSerialState *s = (USBSerialState *)dev;
+    USBSerialState *s = USB_SERIAL(dev);
     uint8_t devep = p->ep->nr;
     struct iovec *iov;
     int i;