diff --git a/libraries/AP_HAL_Empty/GPIO.cpp b/libraries/AP_HAL_Empty/GPIO.cpp
index d8053ac094..e9b4a07766 100644
--- a/libraries/AP_HAL_Empty/GPIO.cpp
+++ b/libraries/AP_HAL_Empty/GPIO.cpp
@@ -28,8 +28,9 @@ AP_HAL::DigitalSource* GPIO::channel(uint16_t n) {
 }
 
 /* Interrupt interface: */
-bool GPIO::attach_interrupt(uint8_t interrupt_num, AP_HAL::Proc p,
-        uint8_t mode) {
+bool GPIO::attach_interrupt(uint8_t interrupt_num,
+                            irq_handler_fn_t fn,
+                            INTERRUPT_TRIGGER_TYPE mode) {
     return true;
 }
 
diff --git a/libraries/AP_HAL_Empty/GPIO.h b/libraries/AP_HAL_Empty/GPIO.h
index dc01d34761..05a4798bae 100644
--- a/libraries/AP_HAL_Empty/GPIO.h
+++ b/libraries/AP_HAL_Empty/GPIO.h
@@ -15,8 +15,9 @@ public:
     AP_HAL::DigitalSource* channel(uint16_t n);
 
     /* Interrupt interface: */
-    bool    attach_interrupt(uint8_t interrupt_num, AP_HAL::Proc p,
-            uint8_t mode);
+    bool    attach_interrupt(uint8_t interrupt_num,
+                             irq_handler_fn_t fn,
+                             INTERRUPT_TRIGGER_TYPE mode) override;
 
     /* return true if USB cable is connected */
     bool    usb_connected(void);