diff --git a/ChangeLog b/ChangeLog
index 17c6fbe20b..19b6bc7ca1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun May  9 23:07:53 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* proc.c (proc_dup): copy blockprocval.  proc_dup is used by
+	  define_method, which made blockprocval be GC'ed mistakenly.
+	  [ruby-core:30023]
+
 Sun May  9 16:28:15 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* cont.c (fiber_initialize_machine_stack_context): try to release
diff --git a/proc.c b/proc.c
index 30fc2475a6..81ec03d954 100644
--- a/proc.c
+++ b/proc.c
@@ -105,6 +105,7 @@ proc_dup(VALUE self)
 
     dst->block = src->block;
     dst->block.proc = procval;
+    dst->blockprocval = src->blockprocval;
     dst->envval = src->envval;
     dst->safe_level = src->safe_level;
     dst->is_lambda = src->is_lambda;