diff --git a/multi_button.c b/multi_button.c
index 1061e68..6b09dc8 100644
--- a/multi_button.c
+++ b/multi_button.c
@@ -18,7 +18,7 @@ static struct Button* head_handle = NULL;
   * @param  button_id: the button id.
   * @retval None
   */
-void button_init(struct Button* handle, uint8_t(*pin_level)(), uint8_t active_level, uint8_t button_id)
+void button_init(struct Button* handle, uint8_t(*pin_level)(uint8_t), uint8_t active_level, uint8_t button_id)
 {
 	memset(handle, 0, sizeof(struct Button));
 	handle->event = (uint8_t)NONE_PRESS;
diff --git a/multi_button.h b/multi_button.h
index b066ade..c468458 100644
--- a/multi_button.h
+++ b/multi_button.h
@@ -48,7 +48,7 @@ typedef struct Button {
 extern "C" {
 #endif
 
-void button_init(struct Button* handle, uint8_t(*pin_level)(), uint8_t active_level, uint8_t button_id);
+void button_init(struct Button* handle, uint8_t(*pin_level)(uint8_t), uint8_t active_level, uint8_t button_id);
 void button_attach(struct Button* handle, PressEvent event, BtnCallback cb);
 PressEvent get_button_event(struct Button* handle);
 int  button_start(struct Button* handle);