diff --git a/core/mutex.c b/core/mutex.c
index 72b6bc5fcb..6c8db0385e 100644
--- a/core/mutex.c
+++ b/core/mutex.c
@@ -49,7 +49,9 @@
  * therefore, beneficial for the majority of applications.
  */
 static inline __attribute__((always_inline))
-void _block(mutex_t *mutex, uinttxtptr_t pc)
+void _block(mutex_t *mutex,
+            unsigned irq_state,
+            uinttxtptr_t pc)
 {
     /* pc is only used when MODULE_CORE_MUTEX_DEBUG */
     (void)pc;
@@ -85,7 +87,7 @@ void _block(mutex_t *mutex, uinttxtptr_t pc)
     }
 #endif
 
-    irq_enable();
+    irq_restore(irq_state);
     thread_yield_higher();
     /* We were woken up by scheduler. Waker removed us from queue. */
 #if IS_USED(MODULE_CORE_MUTEX_DEBUG)
@@ -95,12 +97,11 @@ void _block(mutex_t *mutex, uinttxtptr_t pc)
 
 bool mutex_lock_internal(mutex_t *mutex, bool block)
 {
-    assert(irq_is_enabled());
     uinttxtptr_t pc = 0;
 #if IS_USED(MODULE_CORE_MUTEX_DEBUG)
     pc = cpu_get_caller_pc();
 #endif
-    irq_disable();
+    unsigned irq_state = irq_disable();
 
     DEBUG("PID[%" PRIkernel_pid "] mutex_lock_internal(block=%u).\n",
           thread_getpid(), (unsigned)block);
@@ -121,14 +122,14 @@ bool mutex_lock_internal(mutex_t *mutex, bool block)
 #endif
         DEBUG("PID[%" PRIkernel_pid "] mutex_lock(): early out.\n",
               thread_getpid());
-        irq_enable();
+        irq_restore(irq_state);
     }
     else {
         if (!block) {
-            irq_enable();
+            irq_restore(irq_state);
             return false;
         }
-        _block(mutex, pc);
+        _block(mutex, irq_state, pc);
     }
 
     return true;
@@ -136,12 +137,11 @@ bool mutex_lock_internal(mutex_t *mutex, bool block)
 
 int mutex_lock_cancelable(mutex_cancel_t *mc)
 {
-    assert(irq_is_enabled());
     uinttxtptr_t pc = 0;
 #if IS_USED(MODULE_CORE_MUTEX_DEBUG)
     pc = cpu_get_caller_pc();
 #endif
-    irq_disable();
+    unsigned irq_state = irq_disable();
 
     DEBUG("PID[%" PRIkernel_pid "] mutex_lock_cancelable()\n",
           thread_getpid());
@@ -149,7 +149,7 @@ int mutex_lock_cancelable(mutex_cancel_t *mc)
     if (mc->cancelled) {
         DEBUG("PID[%" PRIkernel_pid "] mutex_lock_cancelable cancelled "
               "early.\n", thread_getpid());
-        irq_enable();
+        irq_restore(irq_state);
         return -ECANCELED;
     }
 
@@ -171,11 +171,11 @@ int mutex_lock_cancelable(mutex_cancel_t *mc)
 #endif
         DEBUG("PID[%" PRIkernel_pid "] mutex_lock_cancelable() early out.\n",
               thread_getpid());
-        irq_enable();
+        irq_restore(irq_state);
         return 0;
     }
     else {
-        _block(mutex, pc);
+        _block(mutex, irq_state, pc);
         if (mc->cancelled) {
             DEBUG("PID[%" PRIkernel_pid "] mutex_lock_cancelable() "
                   "cancelled.\n", thread_getpid());
@@ -237,10 +237,9 @@ void mutex_unlock(mutex_t *mutex)
 
 void mutex_unlock_and_sleep(mutex_t *mutex)
 {
-    assert(irq_is_enabled());
     DEBUG("PID[%" PRIkernel_pid "] mutex_unlock_and_sleep(): queue.next: %p\n",
           thread_getpid(), (void *)mutex->queue.next);
-    irq_disable();
+    unsigned irqstate = irq_disable();
 
     if (mutex->queue.next) {
         if (mutex->queue.next == MUTEX_LOCKED) {
@@ -262,7 +261,7 @@ void mutex_unlock_and_sleep(mutex_t *mutex)
     DEBUG("PID[%" PRIkernel_pid "] mutex_unlock_and_sleep(): going to sleep.\n",
           thread_getpid());
     sched_set_status(thread_get_active(), STATUS_SLEEPING);
-    irq_enable();
+    irq_restore(irqstate);
     thread_yield_higher();
 }
 
diff --git a/sys/evtimer/evtimer.c b/sys/evtimer/evtimer.c
index 90a5f90f81..a8f8132446 100644
--- a/sys/evtimer/evtimer.c
+++ b/sys/evtimer/evtimer.c
@@ -125,7 +125,7 @@ static void _update_head_offset(evtimer_t *evtimer)
 
 void evtimer_add(evtimer_t *evtimer, evtimer_event_t *event)
 {
-    irq_disable();
+    unsigned state = irq_disable();
 
     DEBUG("evtimer_add(): adding event with offset %" PRIu32 "\n", event->offset);
 
@@ -134,7 +134,7 @@ void evtimer_add(evtimer_t *evtimer, evtimer_event_t *event)
     if (evtimer->events == event) {
         _set_timer(evtimer);
     }
-    irq_enable();
+    irq_restore(state);
     if (sched_context_switch_request) {
         thread_yield_higher();
     }