diff --git a/babblesim/core/src/irq_handler.c b/babblesim/core/src/irq_handler.c
index d29797500..05eb881a6 100644
--- a/babblesim/core/src/irq_handler.c
+++ b/babblesim/core/src/irq_handler.c
@@ -22,6 +22,12 @@ extern void (* const systemVectors[256])(void);
  * handler and therefore its priority handling
  */
 
+int
+os_arch_in_isr(void)
+{
+    return currently_running_irq >= 0;
+}
+
 void posix_interrupt_raised(void)
 {
     uint64_t irq_lock;
diff --git a/babblesim/hw/bsp/nrf52_bsim/include/os/os_arch.h b/babblesim/hw/bsp/nrf52_bsim/include/os/os_arch.h
index 32bc97bcb..574f1e813 100644
--- a/babblesim/hw/bsp/nrf52_bsim/include/os/os_arch.h
+++ b/babblesim/hw/bsp/nrf52_bsim/include/os/os_arch.h
@@ -48,11 +48,8 @@ void os_arch_frame_init(struct stack_frame *sf);
 #define OS_IDLE_STACK_SIZE (4000)
 #endif
 
-static inline int
-os_arch_in_isr(void)
-{
-	return hw_irq_ctrl_get_irq_status();
-}
+/* Implemented in irq_handler */
+int os_arch_in_isr(void);
 
 /* Include common arch definitions and APIs */
 #include "os/arch/common.h"