diff --git a/src/Makefile b/src/Makefile
index 5161c19..90f5709 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -5,7 +5,7 @@ PROJECT = gnuk
 
 CHOPSTX = ../chopstx
 
-CSRC = main.c call-rsa.c mcu-stm32f103.c \
+CSRC = main.c call-rsa.c \
 	usb_desc.c usb_ctrl.c \
 	usb-ccid.c openpgp.c ac.c openpgp-do.c flash.c \
 	bn.c mod.c \
@@ -43,6 +43,10 @@ ifeq ($(ENABLE_PINPAD),dnd)
 CSRC += usb-msc.c
 endif
 
+ifeq ($(CHIP),stm32f103)
+CSRC += mcu-stm32f103.c 
+endif
+
 ###################################
 CC   = $(CROSS)gcc
 LD   = $(CROSS)gcc
diff --git a/src/stdlib.h b/src/stdlib.h
index 7dcaf03..bc2d05b 100644
--- a/src/stdlib.h
+++ b/src/stdlib.h
@@ -7,9 +7,7 @@
  * For GNU/Linux emulation, we can use C library.
  */
 
-typedef unsigned long int size_t;
-
-#include <stddef.h> /* NULL */
+#include <stddef.h> /* NULL and size_t */
 
 #define malloc(size)	gnuk_malloc (size)
 #define free(p)		gnuk_free (p)