diff --git a/spybug/sys.cpp b/spybug/sys.cpp
index fb31e04..c741e53 100644
--- a/spybug/sys.cpp
+++ b/spybug/sys.cpp
@@ -3,6 +3,8 @@
 
 #include "sys.hh"
 
+void (*full_reset)() = nullptr;
+
 static volatile bool wdt_int_sleep_mode = false;
 ISR (WDT_vect) {
 	if (wdt_int_sleep_mode)
diff --git a/spybug/sys.hh b/spybug/sys.hh
index d89742f..44a256c 100644
--- a/spybug/sys.hh
+++ b/spybug/sys.hh
@@ -8,7 +8,7 @@
 #include <avr/wdt.h>
 #include <avr/sleep.h>
 
-static void (*full_reset)() = nullptr;
+extern void (*full_reset)();
 
 void low_power_sleep_minutes(unsigned long t);