diff --git a/include/common/debug.h b/include/common/debug.h
index a8dcb8d..d198c32 100644
--- a/include/common/debug.h
+++ b/include/common/debug.h
@@ -84,6 +84,6 @@
 void __dead2 do_panic(void);
 #define panic()	do_panic()
 
-void tf_printf(const char *fmt, ...);
+void tf_printf(const char *fmt, ...) __printflike(1, 2);
 
 #endif /* __DEBUG_H__ */
diff --git a/include/stdlib/stdio.h b/include/stdlib/stdio.h
index 60e081b..57e5c7f 100644
--- a/include/stdlib/stdio.h
+++ b/include/stdlib/stdio.h
@@ -58,12 +58,13 @@
 
 #define	EOF	(-1)
 
-int	 printf(const char * __restrict, ...);
+int	 printf(const char * __restrict, ...) __printflike(1, 2);
 int	 putchar(int);
 int	 puts(const char *);
-int	 sprintf(char * __restrict, const char * __restrict, ...);
+int	 sprintf(char * __restrict, const char * __restrict, ...)
+	__printflike(2, 3);
 int	 vsprintf(char * __restrict, const char * __restrict,
-	   __va_list);
+	   __va_list) __printflike(2, 0);
 
 int	 sscanf(const char *__restrict, char const *__restrict, ...);