diff --git a/libraries/AP_HAL_AVR/utility/ISRRegistry.cpp b/libraries/AP_HAL_AVR/utility/ISRRegistry.cpp
index ce15166dc4..49aba388ab 100644
--- a/libraries/AP_HAL_AVR/utility/ISRRegistry.cpp
+++ b/libraries/AP_HAL_AVR/utility/ISRRegistry.cpp
@@ -6,13 +6,7 @@
 
 using namespace AP_HAL_AVR;
 
-proc_ptr ISRRegistry::_registry[ISR_REGISTRY_NUM_SLOTS];
-
-void ISRRegistry::init() {
-    for(int i = 0; i < ISR_REGISTRY_NUM_SLOTS; i++) {
-        _registry[i] = NULL;
-    }
-}
+proc_ptr ISRRegistry::_registry[ISR_REGISTRY_NUM_SLOTS] = {NULL};
 
 int ISRRegistry::register_signal(int signal, proc_ptr proc)
 {
diff --git a/libraries/AP_HAL_AVR/utility/ISRRegistry.h b/libraries/AP_HAL_AVR/utility/ISRRegistry.h
index c6aff5ae94..3882776d8d 100644
--- a/libraries/AP_HAL_AVR/utility/ISRRegistry.h
+++ b/libraries/AP_HAL_AVR/utility/ISRRegistry.h
@@ -14,7 +14,6 @@ typedef void (*proc_ptr)(void);
 
 class AP_HAL_AVR::ISRRegistry {
 public:
-    void init();
     int register_signal(int isr_number, proc_ptr proc);
     int unregister_signal(int isr_number);