diff --git a/include/mimalloc/atomic.h b/include/mimalloc/atomic.h
index d2711019..3a0d4892 100644
--- a/include/mimalloc/atomic.h
+++ b/include/mimalloc/atomic.h
@@ -441,13 +441,13 @@ static inline void mi_lock_release(mi_lock_t* lock) {
   pthread_mutex_unlock(lock);
 }
 static inline void mi_lock_init(mi_lock_t* lock) {
-  (void)(lock);
+  pthread_mutex_init(lock, NULL);
 }
 static inline void mi_lock_done(mi_lock_t* lock) {
-  (void)(lock);
+  pthread_mutex_destroy(lock);
 }
 
-
+/*
 #elif defined(__cplusplus)
 
 #include <mutex>
@@ -469,6 +469,7 @@ static inline void mi_lock_init(mi_lock_t* lock) {
 static inline void mi_lock_done(mi_lock_t* lock) {
   (void)(lock);
 }
+*/
 
 #else
 
diff --git a/src/arena.c b/src/arena.c
index 24f1299c..7d7eb089 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -863,7 +863,7 @@ void _mi_arena_field_cursor_init(mi_heap_t* heap, mi_subproc_t* subproc, mi_aren
     current->start = (heap == NULL || max_arena == 0 ? 0 : (mi_arena_id_t)(_mi_heap_random_next(heap) % max_arena));
     current->end   = current->start + max_arena;
   }
-  mi_assert_internal(current->start < max_arena);
+  mi_assert_internal(current->start <= max_arena);
 }
 
 static mi_segment_t* mi_arena_segment_clear_abandoned_at(mi_arena_t* arena, mi_subproc_t* subproc, mi_bitmap_index_t bitmap_idx) {