diff --git a/src/ar65/error.h b/src/ar65/error.h
index be36010f5..1f6823269 100644
--- a/src/ar65/error.h
+++ b/src/ar65/error.h
@@ -38,6 +38,11 @@
 
 
 
+/* common */
+#include "attrib.h"
+
+
+
 /*****************************************************************************/
 /*	  		   	     Data		     		     */
 /*****************************************************************************/
@@ -57,13 +62,13 @@ extern const char _MsgFail [];
 
 
 
-void Warning (const char* Format, ...);
+void Warning (const char* Format, ...) attribute((format(printf,1,2)));
 /* Print a warning message */
 
-void Error (const char* Format, ...);
+void Error (const char* Format, ...) attribute((format(printf,1,2)));
 /* Print an error message and die */
 
-void Internal (const char* Format, ...);
+void Internal (const char* Format, ...) attribute((format(printf,1,2)));
 /* Print an internal error message and die */
 
 #define CHECK(c)     							\
diff --git a/src/ar65/make/gcc.mak b/src/ar65/make/gcc.mak
index 1f99cb2a0..2333108c2 100644
--- a/src/ar65/make/gcc.mak
+++ b/src/ar65/make/gcc.mak
@@ -2,7 +2,7 @@
 # gcc Makefile for ar65
 #
 
-CFLAGS 	= -g -O2 -Wall
+CFLAGS 	= -g -O2 -Wall -I../common
 CC	= gcc
 LDFLAGS	=