diff --git a/fs_defs.h b/fs_defs.h
index 588f0c0..cc4cce0 100644
--- a/fs_defs.h
+++ b/fs_defs.h
@@ -22,6 +22,8 @@ extern "C" {
 #define FS_RET_NO_ERROR                 0x0000
 #define FS_RET_ALL_ERROR                (u32)(-1)
 
+#define FS_IO_BUFFER_ALIGN              64
+
 #define FS_STAT_FLAG_IS_DIRECTORY       0x80000000
 
 /* max length of file/dir name */