diff --git a/inc/fdb_low_lvl.h b/inc/fdb_low_lvl.h
index 160db75..b2cdd0d 100644
--- a/inc/fdb_low_lvl.h
+++ b/inc/fdb_low_lvl.h
@@ -29,7 +29,7 @@
 /* Return the most contiguous size aligned at specified width. RT_ALIGN(13, 4)
  * would return 16.
  */
-#define FDB_ALIGN(size, align)                    (((size) + (align) - 1) & ~((align) - 1))
+#define FDB_ALIGN(size, align)                    ((size + align - 1) - ((size + align -1) % align))
 /* align by write granularity */
 #define FDB_WG_ALIGN(size)                        (FDB_ALIGN(size, (FDB_WRITE_GRAN + 7)/8))
 /**