diff --git a/cores/arduino/USBAPI.h b/cores/arduino/USBAPI.h
index 1c21845..d5abdb6 100644
--- a/cores/arduino/USBAPI.h
+++ b/cores/arduino/USBAPI.h
@@ -65,7 +65,7 @@ public:
 	void move(signed char x, signed char y, signed char wheel = 0);	
 	void press(uint8_t b = MOUSE_LEFT);		// press LEFT by default
 	void release(uint8_t b = MOUSE_LEFT);	// release LEFT by default
-	bool isPressed(uint8_t b = MOUSE_ALL);	// check all buttons by default
+	bool isPressed(uint8_t b = MOUSE_LEFT);	// check LEFT by default
 };
 extern Mouse_ Mouse;