diff --git a/src/bus.h b/src/bus.h
index bd98776..b3f6d4e 100644
--- a/src/bus.h
+++ b/src/bus.h
@@ -18,8 +18,8 @@ typedef struct bus_tag bus_t;
 
 uint8_t bus_read_1(bus_t *, uint16_t);
 void bus_write_1(bus_t *, uint16_t, uint8_t);
-bus_t bus_init();
-bus_t bus_init_with_default_devs();
+bus_t bus_init(void);
+bus_t bus_init_with_default_devs(void);
 void bus_finish(bus_t *);
 bool bus_load_file(bus_t *, uint16_t, const char *);
 bool bus_load_buf(bus_t *, uint16_t, uint8_t *, uint16_t);