Index: uspace/lib/usbvirt/transaction.c
===================================================================
--- uspace/lib/usbvirt/transaction.c	(revision aab02fb0aba3474bbfbd4ecfa9d29b503cb256e3)
+++ uspace/lib/usbvirt/transaction.c	(revision d08b1603eb7df6e5cbfe87e42734e2f7139e66ef)
@@ -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);