Index: /trunk/src/VBox/Devices/USB/VUSBDevice.cpp
===================================================================
--- /trunk/src/VBox/Devices/USB/VUSBDevice.cpp	(revision 59858)
+++ /trunk/src/VBox/Devices/USB/VUSBDevice.cpp	(revision 59859)
@@ -663,5 +663,6 @@
         uint32_t cbSrc_ = cbSrc; \
         uint32_t cbCopy = RT_MIN(cbLeft, cbSrc_); \
-        memcpy(pbBuf, pvSrc, cbCopy); \
+        if (cbCopy) \
+            memcpy(pbBuf, pvSrc, cbCopy); \
         cbLeft -= cbCopy; \
         if (!cbLeft) \