Index: /trunk/src/VBox/Storage/VD.cpp
===================================================================
--- /trunk/src/VBox/Storage/VD.cpp	(revision 64711)
+++ /trunk/src/VBox/Storage/VD.cpp	(revision 64712)
@@ -7013,7 +7013,10 @@
                            ("cbSize=%llu\n", cbSize),
                            rc = VERR_INVALID_PARAMETER);
-        AssertMsgBreakStmt(!(cbSize % 512),
-                           ("cbSize=%llu\n", cbSize),
-                           rc = VERR_VD_INVALID_SIZE);
+        if (cbSize % 512)
+        {
+            rc = vdError(pDisk, VERR_VD_INVALID_SIZE, RT_SRC_POS,
+                         N_("VD: The given disk size %llu is not aligned on a sector boundary (512 bytes)"), cbSize);
+            break;
+        }
         AssertMsgBreakStmt(   ((uImageFlags & ~VD_IMAGE_FLAGS_MASK) == 0)
                            || ((uImageFlags & (VD_IMAGE_FLAGS_FIXED | VD_IMAGE_FLAGS_DIFF)) != VD_IMAGE_FLAGS_FIXED),