Index: /trunk/src/VBox/Devices/Storage/VHDHDDCore.cpp
===================================================================
--- /trunk/src/VBox/Devices/Storage/VHDHDDCore.cpp	(revision 31378)
+++ /trunk/src/VBox/Devices/Storage/VHDHDDCore.cpp	(revision 31379)
@@ -637,5 +637,5 @@
         {
             /* Undo and restore the old value. */
-            pImage->pBlockAllocationTable[pExpand->idxBatAllocated] == ~0U;
+            pImage->pBlockAllocationTable[pExpand->idxBatAllocated] = ~0U;
 
             /* Restore the old value on the disk.