diff --git a/examples/NonArduino/Tock/libtockHal.h b/examples/NonArduino/Tock/libtockHal.h
index 85c53920..f4c92118 100644
--- a/examples/NonArduino/Tock/libtockHal.h
+++ b/examples/NonArduino/Tock/libtockHal.h
@@ -55,6 +55,8 @@
 
 typedef void (*gpioIrqFn)(void);
 
+gpioIrqFn gpio_funcs[4] = { NULL, NULL, NULL, NULL};
+
 /*
  * Get the the timer frequency in Hz.
  */
@@ -73,7 +75,7 @@ static void lora_phy_gpio_Callback (int gpioPin,
                                     __attribute__ ((unused)) int arg3,
                                     void* userdata)
 {
-    gpioIrqFn fn = *(gpioIrqFn*)(&userdata);
+    gpioIrqFn fn = gpio_funcs[gpioPin - 1];
 
     if (fn != NULL ) {
         fn();
@@ -136,7 +138,8 @@ class TockHal : public RadioLibHal {
         return;
       }
 
-      libtock_lora_phy_gpio_command_interrupt_callback(lora_phy_gpio_Callback, &interruptCb);
+      gpio_funcs[interruptNum - 1] = interruptCb;
+      libtock_lora_phy_gpio_command_interrupt_callback(lora_phy_gpio_Callback, NULL);
 
       // set GPIO as input and enable interrupts on it
       libtock_lora_phy_gpio_enable_input(interruptNum, libtock_pull_down);
@@ -148,6 +151,7 @@ class TockHal : public RadioLibHal {
         return;
       }
 
+      gpio_funcs[interruptNum - 1] = NULL;
       libtock_lora_phy_gpio_disable_interrupt(interruptNum);
     }