diff --git a/core/Makefile b/core/Makefile
index 71b42a2..7ec0cba 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -623,6 +623,10 @@
 mkyaffs2_extra_flags :=
 endif
 
+ifneq ($(BOARD_NAND_SPARE_SIZE),)
+mkyaffs2_extra_flags += -s $(BOARD_NAND_SPARE_SIZE)
+endif
+
 
 # -----------------------------------------------------------------
 # system yaffs image