diff --git a/ChangeLog b/ChangeLog
index 6174de2d..055b38ba 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2008-05-13  Tatsuhiro Tsujikawa  <tujikawa at rednoah dot com>
+
+	Made string literal to static const std::string
+	* src/BtChokeMessage.cc (toString)
+	* src/BtHaveAllMessage.cc (toString)
+	* src/BtHaveNoneMessage.cc (toString)
+	* src/BtInterestedMessage.cc (toString)
+	* src/BtNotInterestedMessage.cc (toString)
+	* src/BtUnchokeMessage.cc (toString)
+
 2008-05-13  Tatsuhiro Tsujikawa  <tujikawa at rednoah dot com>
 
 	Replaced "" with static const variable A2STR::NIL.
diff --git a/src/BtChokeMessage.cc b/src/BtChokeMessage.cc
index e3d5bc6e..e158ebbc 100644
--- a/src/BtChokeMessage.cc
+++ b/src/BtChokeMessage.cc
@@ -92,7 +92,8 @@ void BtChokeMessage::onSendComplete() {
 }
 
 std::string BtChokeMessage::toString() const {
-  return "choke";
+  static const std::string CHOKE("choke");
+  return CHOKE;
 }
 
 } // namespace aria2
diff --git a/src/BtHaveAllMessage.cc b/src/BtHaveAllMessage.cc
index 14469de7..38c763bf 100644
--- a/src/BtHaveAllMessage.cc
+++ b/src/BtHaveAllMessage.cc
@@ -87,7 +87,8 @@ size_t BtHaveAllMessage::getMessageLength() {
 }
 
 std::string BtHaveAllMessage::toString() const {
-  return "have all";
+  static const std::string HAVE_ALL("have all");
+  return HAVE_ALL;
 }
 
 } // namespace aria2
diff --git a/src/BtHaveNoneMessage.cc b/src/BtHaveNoneMessage.cc
index 04d16325..17eec5ca 100644
--- a/src/BtHaveNoneMessage.cc
+++ b/src/BtHaveNoneMessage.cc
@@ -83,7 +83,8 @@ size_t BtHaveNoneMessage::getMessageLength() {
 }
 
 std::string BtHaveNoneMessage::toString() const {
-  return "have none";
+  static const std::string HAVE_NONE("have none");
+  return HAVE_NONE;
 }
 
 } // namespace aria2
diff --git a/src/BtInterestedMessage.cc b/src/BtInterestedMessage.cc
index 3e63b2f2..aab9a612 100644
--- a/src/BtInterestedMessage.cc
+++ b/src/BtInterestedMessage.cc
@@ -93,7 +93,8 @@ void BtInterestedMessage::onSendComplete() {
 }
 
 std::string BtInterestedMessage::toString() const {
-  return "interested";
+  static const std::string INTERESTED("interested");
+  return INTERESTED;
 }
 
 } // namespace aria2
diff --git a/src/BtNotInterestedMessage.cc b/src/BtNotInterestedMessage.cc
index a93e1faf..f9548e45 100644
--- a/src/BtNotInterestedMessage.cc
+++ b/src/BtNotInterestedMessage.cc
@@ -93,7 +93,8 @@ void BtNotInterestedMessage::onSendComplete() {
 }
 
 std::string BtNotInterestedMessage::toString() const {
-  return "not interested";
+  static const std::string NOT_INTERESTED("not interested");
+  return NOT_INTERESTED;
 }
 
 } // namespace aria2
diff --git a/src/BtUnchokeMessage.cc b/src/BtUnchokeMessage.cc
index 87057f30..40327e4b 100644
--- a/src/BtUnchokeMessage.cc
+++ b/src/BtUnchokeMessage.cc
@@ -87,7 +87,8 @@ void BtUnchokeMessage::onSendComplete() {
 }
 
 std::string BtUnchokeMessage::toString() const {
-  return "unchoke";
+  static const std::string UNCHOKE("unchoke");
+  return UNCHOKE;
 }
 
 } // namespace aria2