diff --git a/gecko.h b/gecko.h
index a949525..c9a4e22 100644
--- a/gecko.h
+++ b/gecko.h
@@ -12,7 +12,7 @@ int gecko_sendbuffer_safe(const void *buffer, u32 size);
 int gecko_putchar(int c);
 int gecko_getchar(void);
 int gecko_puts(const char *s);
-int gecko_printf( const char *fmt, ...);
+int gecko_printf( const char *fmt, ...) __attribute__((format (printf, 1, 2)));
 void gecko_init(void);
 
 #endif