diff --git a/libusbhost/include/usbhost/usbhost.h b/libusbhost/include/usbhost/usbhost.h
index 88b5b44..84594c8 100644
--- a/libusbhost/include/usbhost/usbhost.h
+++ b/libusbhost/include/usbhost/usbhost.h
@@ -216,7 +216,7 @@
 int usb_device_bulk_transfer(struct usb_device *device,
                             int endpoint,
                             void* buffer,
-                            int length,
+                            unsigned int length,
                             unsigned int timeout);
 
 /** Reset USB bus for the device */
diff --git a/libusbhost/usbhost.c b/libusbhost/usbhost.c
index 299fdc4..68aca17 100644
--- a/libusbhost/usbhost.c
+++ b/libusbhost/usbhost.c
@@ -600,7 +600,7 @@
 int usb_device_bulk_transfer(struct usb_device *device,
                             int endpoint,
                             void* buffer,
-                            int length,
+                            unsigned int length,
                             unsigned int timeout)
 {
     struct usbdevfs_bulktransfer  ctrl;