1 files changed, 2 insertions, 0 deletions
diff --git a/thread.c b/thread.c
index 20e3deacdd..0cf48e38c6 100644
--- a/thread.c
+++ b/thread.c
@@ -4217,6 +4217,8 @@ 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++;
+
     vm->sleeper = 0;
     clear_coverage();
 }