diff --git a/nimble/include/nimble/nimble_npl.h b/nimble/include/nimble/nimble_npl.h
index 7f17e3f23..49505958d 100644
--- a/nimble/include/nimble/nimble_npl.h
+++ b/nimble/include/nimble/nimble_npl.h
@@ -157,7 +157,7 @@ void ble_npl_time_delay(ble_npl_time_t ticks);
 
 #if NIMBLE_CFG_CONTROLLER
 
-void ble_npl_hw_set_isr(int irqn, void (*addr)());
+void ble_npl_hw_set_isr(int irqn, void (*addr)(void));
 
 #endif
 
diff --git a/porting/npl/freertos/include/nimble/nimble_npl_os.h b/porting/npl/freertos/include/nimble/nimble_npl_os.h
index 68aaefe40..00f64ba2d 100644
--- a/porting/npl/freertos/include/nimble/nimble_npl_os.h
+++ b/porting/npl/freertos/include/nimble/nimble_npl_os.h
@@ -272,7 +272,7 @@ ble_npl_time_delay(ble_npl_time_t ticks)
 
 #if NIMBLE_CFG_CONTROLLER
 static inline void
-ble_npl_hw_set_isr(int irqn, void (*addr)())
+ble_npl_hw_set_isr(int irqn, void (*addr)(void))
 {
     npl_freertos_hw_set_isr(irqn, addr);
 }
diff --git a/porting/npl/freertos/include/nimble/npl_freertos.h b/porting/npl/freertos/include/nimble/npl_freertos.h
index 3155c588b..a7b1c4aa7 100644
--- a/porting/npl/freertos/include/nimble/npl_freertos.h
+++ b/porting/npl/freertos/include/nimble/npl_freertos.h
@@ -65,7 +65,7 @@ ble_npl_error_t npl_freertos_time_ms_to_ticks(uint32_t ms,
 ble_npl_error_t npl_freertos_time_ticks_to_ms(ble_npl_time_t ticks,
                                               uint32_t *out_ms);
 
-void npl_freertos_hw_set_isr(int irqn, void (*addr)());
+void npl_freertos_hw_set_isr(int irqn, void (*addr)(void));
 
 uint32_t npl_freertos_hw_enter_critical(void);
 
diff --git a/porting/npl/riot/src/nrf5x_isr.c b/porting/npl/riot/src/nrf5x_isr.c
index ee38ed6e6..01ba23483 100644
--- a/porting/npl/riot/src/nrf5x_isr.c
+++ b/porting/npl/riot/src/nrf5x_isr.c
@@ -19,9 +19,9 @@
 
 #include "cpu.h"
 
-static void (*radio_isr_addr)();
-static void (*rng_isr_addr)();
-static void (*rtc0_isr_addr)();
+static void (*radio_isr_addr)(void);
+static void (*rng_isr_addr)(void);
+static void (*rtc0_isr_addr)(void);
 
 void
 isr_radio(void)
@@ -42,7 +42,7 @@ isr_rtc0(void)
 }
 
 void
-ble_npl_hw_set_isr(int irqn, void (*addr)())
+ble_npl_hw_set_isr(int irqn, void (*addr)(void))
 {
     switch (irqn) {
     case RADIO_IRQn: