diff --git a/libraries/Ticker/Ticker.cpp b/libraries/Ticker/Ticker.cpp
index 5fa2dc960..b53b429da 100644
--- a/libraries/Ticker/Ticker.cpp
+++ b/libraries/Ticker/Ticker.cpp
@@ -68,7 +68,7 @@ void Ticker::detach()
 	_callback_function = nullptr;
 }
 
-bool Ticker::active()
+bool Ticker::active() const
 {
 	return (bool)_timer;
 }
diff --git a/libraries/Ticker/Ticker.h b/libraries/Ticker/Ticker.h
index d006c8ffc..15474594f 100644
--- a/libraries/Ticker/Ticker.h
+++ b/libraries/Ticker/Ticker.h
@@ -121,7 +121,7 @@ public:
 	}
 
 	void detach();
-	bool active();
+	bool active() const;
 
 protected:	
 	void _attach_ms(uint32_t milliseconds, bool repeat, callback_with_arg_t callback, uint32_t arg);