Index: /trunk/src/VBox/Devices/Storage/DevAHCI.cpp
===================================================================
--- /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 50035)
+++ /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 50036)
@@ -2416,4 +2416,6 @@
             if (rc == VINF_IOM_R3_MMIO_READ)
                 rc = VINF_IOM_R3_IOPORT_READ;
+            else if (rc == VINF_IOM_MMIO_UNUSED_00)
+                rc = VERR_IOM_IOPORT_UNUSED;
         }
     }