1 files changed, 1 insertions, 0 deletions
diff --git a/eval.c b/eval.c
index 0434917bec..031a57b316 100644
--- a/eval.c
+++ b/eval.c
@@ -13289,6 +13289,7 @@ Init_Thread()
 {
     VALUE cThGroup;
 
+    recursive_key = rb_intern("__recursive_key__");
     rb_eThreadError = rb_define_class("ThreadError", rb_eStandardError);
     rb_cThread = rb_define_class("Thread", rb_cObject);
     rb_undef_alloc_func(rb_cThread);