diff --git a/ChangeLog b/ChangeLog
index 5e538482ea..ff21609e72 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Oct 12 12:03:38 2008  Koichi Sasada  <ko1@atdot.net>
+
+	* vm.c, vm_insnhelper.h (ruby_vm_redefined_flag): apply optimization
+	  patch proposed by Paul Brannan.  [ruby-core:19171]
+
 Sun Oct 12 09:46:36 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* strftime.c (rb_strftime): suppressed warnings on cygwin.
diff --git a/vm.c b/vm.c
index a805c80526..5bf684237e 100644
--- a/vm.c
+++ b/vm.c
@@ -34,7 +34,7 @@ VALUE rb_cEnv;
 VALUE rb_mRubyVMFrozenCore;
 
 VALUE ruby_vm_global_state_version = 1;
-VALUE ruby_vm_redefined_flag = 0;
+char ruby_vm_redefined_flag[BOP_LAST_];
 
 rb_thread_t *ruby_current_thread = 0;
 rb_vm_t *ruby_current_vm = 0;
@@ -877,7 +877,7 @@ rb_vm_check_redefinition_opt_method(const NODE *node)
     VALUE bop;
 
     if (st_lookup(vm_opt_method_table, (st_data_t)node, &bop)) {
-	ruby_vm_redefined_flag |= bop;
+	ruby_vm_redefined_flag[bop] = 1;
     }
 }
 
@@ -902,7 +902,7 @@ vm_init_redefined_flag(void)
 
     vm_opt_method_table = st_init_numtable();
 
-#define OP(mid_, bop_) (mid = id##mid_, bop = BOP_##bop_)
+#define OP(mid_, bop_) (mid = id##mid_, bop = BOP_##bop_, ruby_vm_redefined_flag[bop] = 0)
 #define C(k) add_opt_method(rb_c##k, mid, bop)
     OP(PLUS, PLUS), (C(Fixnum), C(Float), C(String), C(Array));
     OP(MINUS, MINUS), (C(Fixnum));
diff --git a/vm_insnhelper.h b/vm_insnhelper.h
index 1d2bdafdad..83efeda4ba 100644
--- a/vm_insnhelper.h
+++ b/vm_insnhelper.h
@@ -34,32 +34,35 @@
 #define VMDEBUG 3
 #endif
 
-/* VM state version */
+enum {
+  BOP_PLUS,
+  BOP_MINUS,
+  BOP_MULT,
+  BOP_DIV,
+  BOP_MOD,
+  BOP_EQ,
+  BOP_LT,
+  BOP_LE,
+  BOP_LTLT,
+  BOP_AREF,
+  BOP_ASET,
+  BOP_LENGTH,
+  BOP_SUCC,
+  BOP_GT,
+  BOP_GE,
+  BOP_NOT,
+  BOP_NEQ,
 
+  BOP_LAST_,
+};
+
+extern char ruby_vm_redefined_flag[BOP_LAST_];
 extern VALUE ruby_vm_global_state_version;
-extern VALUE ruby_vm_redefined_flag;
 
 #define GET_VM_STATE_VERSION() (ruby_vm_global_state_version)
 #define INC_VM_STATE_VERSION() \
   (ruby_vm_global_state_version = (ruby_vm_global_state_version+1) & 0x8fffffff)
 
-#define BOP_PLUS     0x01
-#define BOP_MINUS    0x02
-#define BOP_MULT     0x04
-#define BOP_DIV      0x08
-#define BOP_MOD      0x10
-#define BOP_EQ       0x20
-#define BOP_LT       0x40
-#define BOP_LE       0x80
-#define BOP_LTLT    0x100
-#define BOP_AREF    0x200
-#define BOP_ASET    0x400
-#define BOP_LENGTH  0x800
-#define BOP_SUCC   0x1000
-#define BOP_GT     0x2000
-#define BOP_GE     0x4000
-#define BOP_NOT    0x8000
-#define BOP_NEQ   0x10000
 
 /**********************************************************/
 /* deal with stack                                        */
@@ -180,7 +183,7 @@ extern VALUE ruby_vm_redefined_flag;
 
 /* optimize insn */
 #define FIXNUM_2_P(a, b) ((a) & (b) & 1)
-#define BASIC_OP_UNREDEFINED_P(op) (LIKELY((ruby_vm_redefined_flag & (op)) == 0))
+#define BASIC_OP_UNREDEFINED_P(op) (LIKELY(ruby_vm_redefined_flag[op] == 0))
 #define HEAP_CLASS_OF(obj) RBASIC(obj)->klass
 
 #define CALL_SIMPLE_METHOD(num, id, recv) do { \