diff --git a/build/libraries/os/ARM7/Makefile b/build/libraries/os/ARM7/Makefile
index 40728093..943368c4 100644
--- a/build/libraries/os/ARM7/Makefile
+++ b/build/libraries/os/ARM7/Makefile
@@ -27,6 +27,9 @@ TWL_CODEGEN_ALL 	?= TRUE
 TWL_PROC		= ARM7
 
 SRCDIR			= ../common .
+INCDIR              = ./include ../common/include \
+                      $(TWLSDK_ROOT)/build/libraries/fatfs/ARM7.TWL/include \
+                      $(TWLSDK_ROOT)/build/libraries/fatfs/ARM7.TWL/include/twl/fatfs/ARM7 \
 
 SRCS			= \
 				os_init_firm.c \