Don't use `th->scheduler` directly because it's not always valid to do so.

1 files changed, 4 insertions, 2 deletions

diff --git a/thread.c b/thread.c
index 81172dc7b1..6cc0a9227e 100644
--- a/thread.c
+++ b/thread.c
@@ -1175,8 +1175,10 @@ thread_join_sleep(VALUE arg)
     }
 
     while (target_th->status != THREAD_KILLED) {
-        if (th->scheduler != Qnil) {
-            rb_scheduler_block(th->scheduler, target_th->self, p->timeout);
+        VALUE scheduler = rb_thread_current_scheduler();
+
+        if (scheduler != Qnil) {
+            rb_scheduler_block(scheduler, target_th->self, p->timeout);
         } else if (!limit) {
             th->status = THREAD_STOPPED_FOREVER;
             rb_ractor_sleeper_threads_inc(th->ractor);