diff --git a/lib/ff13/Source/diskio.c b/lib/ff13/Source/diskio.c
index 6b90b70580a6c7de712b726172cf8ed8f861924b..cee7f656c2d54d616af069664f161ca7ff789fed 100644
--- a/lib/ff13/Source/diskio.c
+++ b/lib/ff13/Source/diskio.c
@@ -238,7 +238,7 @@ DRESULT disk_ioctl (
                 break;
             case GET_SECTOR_COUNT:
                 /* Mandatory */
-                *((DWORD *)buff) = mx25_size() / SECTOR_SIZE;
+                *((DWORD *)buff) = mx25_size();
                 status = RES_OK;
                 break;
             case GET_BLOCK_SIZE: