1 files changed, 1 insertions, 0 deletions
diff --git a/thread.c b/thread.c
index 1caea4976c..f0ace8326c 100644
--- a/thread.c
+++ b/thread.c
@@ -4216,6 +4216,7 @@ rb_thread_atfork_internal(rb_thread_t *th, void (*atfork)(rb_thread_t *, const r
     }
     rb_vm_living_threads_init(vm);
     rb_vm_living_threads_insert(vm, th);
+    vm->fork_gen++;
     rb_thread_sync_reset_all();
 
     vm->sleeper = 0;