Index: /trunk/src/VBox/Main/src-server/MediumIOImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/MediumIOImpl.cpp	(revision 74823)
+++ /trunk/src/VBox/Main/src-server/MediumIOImpl.cpp	(revision 74824)
@@ -268,6 +268,9 @@
         do
         {
-            size_t cbThisWrite = RT_MIN(pStreamFile->cbFile - pStreamFile->uOffsetLast, sizeof(g_abRTZero64K));
+            size_t cbThisWrite = sizeof(g_abRTZero64K);
             size_t cbWritten = 0;
+
+            if (pStreamFile->cbFile - pStreamFile->uOffsetLast < sizeof(g_abRTZero64K))
+                cbThisWrite = (size_t)(pStreamFile->cbFile - pStreamFile->uOffsetLast);
 
             rc = pStreamFile->pDataStream->i_write(&g_abRTZero64K[0], cbThisWrite, &cbWritten);
@@ -369,6 +372,9 @@
         do
         {
-            size_t cbThisWrite = RT_MIN(uOffset - pStreamFile->uOffsetLast, sizeof(g_abRTZero64K));
+            size_t cbThisWrite = sizeof(g_abRTZero64K);
             size_t cbWritten = 0;
+
+            if (uOffset - pStreamFile->uOffsetLast < sizeof(g_abRTZero64K))
+                cbThisWrite = (size_t)(uOffset - pStreamFile->uOffsetLast);
 
             rc = pStreamFile->pDataStream->i_write(&g_abRTZero64K[0], cbThisWrite, &cbWritten);