diff --git a/src/class/msc/msc_device.c b/src/class/msc/msc_device.c
index 0fd59212..87ebe227 100644
--- a/src/class/msc/msc_device.c
+++ b/src/class/msc/msc_device.c
@@ -1,4 +1,4 @@
-/* 
+/*
  * The MIT License (MIT)
  *
  * Copyright (c) 2019 Ha Thach (tinyusb.org)
@@ -182,11 +182,16 @@ uint8_t rdwr10_validate_cmd(msc_cbw_t const* cbw)
       TU_LOG(MSC_DEBUG, "  SCSI case 8 (Hi <> Do)\r\n");
       status = MSC_CSW_STATUS_PHASE_ERROR;
     }
-    else if ( !block_count )
+    else if ( 0 == block_count )
     {
-      TU_LOG(MSC_DEBUG, "  SCSI case 4 Hi > Dn\r\n");
+      TU_LOG(MSC_DEBUG, "  SCSI case 4 Hi > Dn (READ10) or case 9 Ho > Dn (WRITE10) \r\n");
       status =  MSC_CSW_STATUS_FAILED;
     }
+    else if ( cbw->total_bytes / block_count == 0 )
+    {
+      TU_LOG(MSC_DEBUG, " Computed block size = 0. SCSI case 7 Hi < Di (READ10) or case 13 Ho < Do (WRIT10)\r\n");
+      status = MSC_CSW_STATUS_PHASE_ERROR;
+    }
   }
 
   return status;