diff --git a/src/app/MBPeripherals.h b/src/app/MBPeripherals.h
index 2e9b335..f5b6dab 100644
--- a/src/app/MBPeripherals.h
+++ b/src/app/MBPeripherals.h
@@ -14,6 +14,8 @@
 
 void defaultExtIntIsr(void);
 
+typedef void (*ExtIntIsr)(void);
+
 class MBPeripherals
 {
   public:
@@ -72,7 +74,7 @@ class MBPeripherals
     void _3V3PowerRail(State state);
     const BoardConfig &_boardConfig;
     const RF24 _NRF;
-    const void (*_extIntIsr)(void);
+    ExtIntIsr _extIntIsr;
   
 };