diff --git a/src/arena-abandoned.c b/src/arena-abandoned.c
index 2a7ade72..75e97faf 100644
--- a/src/arena-abandoned.c
+++ b/src/arena-abandoned.c
@@ -82,7 +82,10 @@ static bool mi_arena_segment_os_clear_abandoned(mi_segment_t* segment, bool take
     segment->abandoned_os_prev = NULL;
     mi_atomic_decrement_relaxed(&subproc->abandoned_count);
     mi_atomic_decrement_relaxed(&subproc->abandoned_os_list_count);
-    mi_atomic_store_release(&segment->thread_id, _mi_thread_id());
+    if (take_lock) {
+      // don't set the thread_id when iterating
+      mi_atomic_store_release(&segment->thread_id, _mi_thread_id());
+    }
     reclaimed = true;
   }
   if (take_lock) { mi_lock_release(&segment->subproc->abandoned_os_lock); }
diff --git a/src/segment.c b/src/segment.c
index 7a2d9e8e..7746bd0f 100644
--- a/src/segment.c
+++ b/src/segment.c
@@ -836,6 +836,7 @@ void _mi_segment_page_abandon(mi_page_t* page, mi_segments_tld_t* tld) {
 // Possibly clear pages and check if free space is available
 static bool mi_segment_check_free(mi_segment_t* segment, size_t block_size, bool* all_pages_free)
 {
+  mi_assert_internal(mi_atomic_load_relaxed(&segment->thread_id) == 0);
   bool has_page = false;
   size_t pages_used = 0;
   size_t pages_used_empty = 0;