diff --git a/include/cmrx/algo.h b/include/cmrx/algo.h
index 9eb85154..91bb093b 100644
--- a/include/cmrx/algo.h
+++ b/include/cmrx/algo.h
@@ -95,9 +95,9 @@
  * items rather than allocation size)
  */
 #define ARRAY_DELETE(_ARRAY, _POS, _SIZE) \
-    for (unsigned q = _POS + 1; q < _SIZE; ++q)\
+    for (unsigned _q = _POS + 1; _q < _SIZE; ++_q)\
     {\
-        _ARRAY[q - 1] = _ARRAY[q];\
+        _ARRAY[_q - 1] = _ARRAY[_q];\
     }\
     _SIZE--;
 
@@ -237,7 +237,7 @@ inline uint32_t os_hash_key(uint32_t key)
     const uint32_t mask = (_MAX) - 1;\
     uint32_t pos = hash & mask;\
     uint32_t stride = 1;\
-    while (_HASHTABLE[pos]._KEY != _VALUE && _HASHTABLE[pos]._KEY != HASH_EMPTY) {\
+    while (_HASHTABLE[pos]._KEY != _VALUE && _HASHTABLE[pos]._KEY != (typeof(_HASHTABLE[0]._KEY)) HASH_EMPTY) {\
         pos = (pos + stride) & mask;\
         stride++;\
     }\
diff --git a/src/os/arch/arm/cmsis/arch/assert.h b/src/os/arch/arm/cmsis/arch/assert.h
index 08b38eb5..a6bb8599 100644
--- a/src/os/arch/arm/cmsis/arch/assert.h
+++ b/src/os/arch/arm/cmsis/arch/assert.h
@@ -5,6 +5,7 @@
 if (!(cond)) \
 {\
     asm volatile("BKPT 0xFF\n\t");\
+    __builtin_unreachable();\
 }
 #else
 #   define ASSERT(cond)
diff --git a/src/os/kernel/notify.c b/src/os/kernel/notify.c
index b20cf242..d16a6136 100644
--- a/src/os/kernel/notify.c
+++ b/src/os/kernel/notify.c
@@ -189,7 +189,10 @@ int os_notify_object(const void * object, Event_t event, uint32_t flags)
         txn_id = os_txn_start();
 
         candidate_waiter = os_find_notified_thread_waiter(object);
-        candidate_timer = os_find_timer(os_notification_waiters[candidate_waiter], TIMER_TIMEOUT);
+        if (candidate_waiter < OS_THREADS)
+        {
+            candidate_timer = os_find_timer(os_notification_waiters[candidate_waiter], TIMER_TIMEOUT);
+        }
     } while (os_txn_commit(txn_id, TXN_READWRITE) != E_OK);
 
     if (candidate_waiter < OS_THREADS)
@@ -282,6 +285,17 @@ void cb_syscall_notify_object(const void * object, Thread_t thread, int sleeper,
 
         case EVT_TIMEOUT:
             os_set_syscall_return_value(thread, E_TIMEOUT);
+            for (unsigned q = 0; q < os_notification_waiters_size; ++q)
+            {
+                if (os_notification_waiters[q] == thread)
+                {
+                    ARRAY_DELETE(os_notification_waiters, q, os_notification_waiters_size);
+                    break;
+                }
+            }
+            notified_thread->wait_object = NULL;
+            notified_thread->wait_callback = NULL;
+
             break;
     }
 }
diff --git a/src/os/kernel/sched.c b/src/os/kernel/sched.c
index f6957a2f..0d86cac4 100644
--- a/src/os/kernel/sched.c
+++ b/src/os/kernel/sched.c
@@ -624,6 +624,8 @@ uint32_t os_shutdown(void)
     os_memory_protection_stop();
 
     os_kernel_shutdown();
+
+    __builtin_unreachable();
 }
 
 struct OS_thread_t * os_thread_get(Thread_t thread_id)
diff --git a/src/os/kernel/timer.c b/src/os/kernel/timer.c
index f5ef3a4d..0aa3bb7e 100644
--- a/src/os/kernel/timer.c
+++ b/src/os/kernel/timer.c
@@ -118,7 +118,7 @@ static int do_set_timed_event(Txn_t txn, const unsigned slot, const unsigned int
         sleeper->interval = interval;
 		sleeper->timer_type = type;
 
-		if (sleeper_queue[old_queue_offs].resume_time != next_resume || old_queue_offs == TIMER_INVALID_ID)
+		if (old_queue_offs == TIMER_INVALID_ID || sleeper_queue[old_queue_offs].resume_time != next_resume)
 		{
 			if (old_queue_offs != TIMER_INVALID_ID)
 			{