diff --git a/src/platforms/common/cdcacm.c b/src/platforms/common/cdcacm.c
index 62cc419..ccf6706 100644
--- a/src/platforms/common/cdcacm.c
+++ b/src/platforms/common/cdcacm.c
@@ -517,7 +517,7 @@ static void cdcacm_set_config(usbd_device *dev, uint16_t wValue)
 
 	/* Serial interface */
 	usbd_ep_setup(dev, 0x03, USB_ENDPOINT_ATTR_BULK,
-	              CDCACM_PACKET_SIZE, usbuart_usb_out_cb);
+	              CDCACM_PACKET_SIZE / 2, usbuart_usb_out_cb);
 	usbd_ep_setup(dev, 0x83, USB_ENDPOINT_ATTR_BULK,
 	              CDCACM_PACKET_SIZE, usbuart_usb_in_cb);
 	usbd_ep_setup(dev, 0x84, USB_ENDPOINT_ATTR_INTERRUPT, 16, NULL);