diff --git a/ChangeLog b/ChangeLog
index e7a5ccfd2a..635655a01b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Nov 18 23:02:23 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* proc.c (proc_eq): equivalence check should not done by pointer
+	  comparison, but should be based on iseq contents.   [ruby-dev:37101]
+
 Tue Nov 18 20:30:08 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* lib/net/ftp.rb (Net::FTP#open_socket): SOCKSsocket is obsolete.
diff --git a/proc.c b/proc.c
index 4907d80bbb..b383d85d8e 100644
--- a/proc.c
+++ b/proc.c
@@ -666,12 +666,15 @@ proc_eq(VALUE self, VALUE other)
     }
     else {
 	if (TYPE(other)          == T_DATA &&
-	    RBASIC(other)->klass == rb_cProc &&
-	    CLASS_OF(self)       == CLASS_OF(other)) {
+	    RDATA(other)->dmark  == proc_mark) {
 	    rb_proc_t *p1, *p2;
 	    GetProcPtr(self, p1);
 	    GetProcPtr(other, p2);
-	    if (p1->block.iseq == p2->block.iseq && p1->envval == p2->envval) {
+	    if (p1->envval == p2->envval &&
+		p1->block.iseq->iseq_size == p2->block.iseq->iseq_size &&
+		p1->block.iseq->local_size == p2->block.iseq->local_size &&
+		MEMCMP(p1->block.iseq->iseq, p2->block.iseq->iseq, VALUE,
+		       p1->block.iseq->iseq_size) == 0) {
 		return Qtrue;
 	    }
 	}