Index: uspace/lib/usbvirt/transaction.c
===================================================================
--- uspace/lib/usbvirt/transaction.c	(revision 0a5a9509a7d4cad54e1a7838593a26fb5891ed93)
+++ uspace/lib/usbvirt/transaction.c	(revision 100962316f11f4d28cc4be7eaf39ac3705dc69ca)
@@ -184,4 +184,6 @@
 				actual_size = size;
 			}
+			device->lib_debug(device, 1, USBVIRT_DEBUGTAG_TRANSACTION,
+			    "in transaction: will copy %zu bytes", actual_size);
 			if (actual_size > 0) {
 				memcpy(buffer, transfer->data, actual_size);