diff --git a/ChangeLog b/ChangeLog
index 09eca39a07..f5c542615a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jan  9 15:40:18 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm.c (th_init, ruby_thread_init): initialize root_svar with Qnil,
+	  since lep_svar_place() expects uninitialized svar to be nil, not 0.
+
 Wed Jan  9 13:20:23 2013  Masaki Matsushita  <glass.saga@gmail.com>
 
 	* test/ruby/test_require.rb: improve test for r38744.
diff --git a/vm.c b/vm.c
index 2f8d121456..e6a2a6d84f 100644
--- a/vm.c
+++ b/vm.c
@@ -1930,6 +1930,7 @@ th_init(rb_thread_t *th, VALUE self)
     th->errinfo = Qnil;
     th->last_status = Qnil;
     th->waiting_fd = -1;
+    th->root_svar = Qnil;
 
 #if OPT_CALL_THREADED_CODE
     th->retval = Qundef;
@@ -1949,6 +1950,7 @@ ruby_thread_init(VALUE self)
 
     th->top_wrapper = 0;
     th->top_self = rb_vm_top_self();
+    th->root_svar = Qnil;
     return self;
 }