diff --git a/thread_none.c b/thread_none.c
index aba8782212bf7c..852ee158ced2e8 100644
--- a/thread_none.c
+++ b/thread_none.c
@@ -42,7 +42,7 @@ thread_sched_yield(struct rb_thread_sched *sched, rb_thread_t *th)
 }
 
 void
-rb_thread_sched_init(struct rb_thread_sched *sched)
+rb_thread_sched_init(struct rb_thread_sched *sched, bool atfork)
 {
 }
 
diff --git a/thread_win32.c b/thread_win32.c
index fe794278304ebf..e28cb4d7ea3649 100644
--- a/thread_win32.c
+++ b/thread_win32.c
@@ -148,7 +148,7 @@ thread_sched_yield(struct rb_thread_sched *sched, rb_thread_t *th)
 }
 
 void
-rb_thread_sched_init(struct rb_thread_sched *sched)
+rb_thread_sched_init(struct rb_thread_sched *sched, bool atfork)
 {
     if (GVL_DEBUG) fprintf(stderr, "sched init\n");
     sched->lock = w32_mutex_create();