diff --git a/smoother/avr/interrupt.h b/smoother/avr/interrupt.h
index b90688e..ddbc245 100644
--- a/smoother/avr/interrupt.h
+++ b/smoother/avr/interrupt.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <mbed.h>
+
 #define ISR(f) void f()
-inline void cli() {}
-inline void sei() {}
+inline void cli() {__disable_irq();}
+inline void sei() {__enable_irq();}