diff --git a/src/A2STR.cc b/src/A2STR.cc
index bcd6d76f..790a5329 100644
--- a/src/A2STR.cc
+++ b/src/A2STR.cc
@@ -36,30 +36,10 @@
 
 namespace aria2 {
 
-const std::string A2STR::NIL("");
+namespace A2STR {
 
-const std::string A2STR::SHARP_C("#");
+const std::string NIL("");
 
-const std::string A2STR::CR_C("\r");
-
-const std::string A2STR::LF_C("\n");
-
-const std::string A2STR::CRLF("\r\n");
-
-const std::string A2STR::SLASH_C("/");
-
-const std::string A2STR::DOT_C(".");
-
-const std::string A2STR::COLON_C(":");
-
-const std::string A2STR::SEMICOLON_C(";");
-
-const std::string A2STR::EQUAL_C("=");
-
-const std::string A2STR::UNDERSCORE_C("_");
-
-const std::string A2STR::BACK_SLASH_C("\\");
-
-const std::string A2STR::COMMA_C(",");
+} // namespace A2STR
 
 } // namespace aria2
diff --git a/src/A2STR.h b/src/A2STR.h
index bddb8808..445c946d 100644
--- a/src/A2STR.h
+++ b/src/A2STR.h
@@ -39,36 +39,12 @@
 
 namespace aria2 {
 
-class A2STR {
-private:
-  A2STR();
-public:
-  static const std::string NIL;
+namespace A2STR {
 
-  static const std::string SHARP_C;
+extern const std::string NIL;
 
-  static const std::string CR_C;
+} // namespace A2STR
 
-  static const std::string LF_C;
-
-  static const std::string CRLF;
-
-  static const std::string SLASH_C;
-
-  static const std::string DOT_C;
-
-  static const std::string COLON_C;
-
-  static const std::string SEMICOLON_C;
-
-  static const std::string EQUAL_C;
-
-  static const std::string UNDERSCORE_C;
-
-  static const std::string BACK_SLASH_C;
-
-  static const std::string COMMA_C;
-};
 } // namespace aria2
 
 #endif // D_A2_STR_H
diff --git a/src/Cookie.cc b/src/Cookie.cc
index 5dc8db54..0628bc27 100644
--- a/src/Cookie.cc
+++ b/src/Cookie.cc
@@ -147,7 +147,7 @@ std::string Cookie::toNsCookieFormat() const
 {
   std::stringstream ss;
   if(!hostOnly_) {
-    ss << A2STR::DOT_C;
+    ss << ".";
   }
   ss << domain_ << "\t";
   if(hostOnly_) {
diff --git a/src/File.cc b/src/File.cc
index dab20cbb..4bef6712 100644
--- a/src/File.cc
+++ b/src/File.cc
@@ -216,10 +216,10 @@ std::string File::getDirname() const
     if(name_.empty()) {
       return A2STR::NIL;
     } else {
-      return A2STR::DOT_C;
+      return ".";
     }
   } else if(lastSlashIndex == 0) {
-    return A2STR::SLASH_C;
+    return "/";
   } else {
     return name_.substr(0, lastSlashIndex);
   }
@@ -281,7 +281,7 @@ std::string File::getCurrentDir()
   if(_wgetcwd(buf, buflen)) {
     return wCharToUtf8(buf);
   } else {
-    return A2STR::DOT_C;
+    return ".";
   }
 #else // !__MINGW32__
   const size_t buflen = 2048;
@@ -289,7 +289,7 @@ std::string File::getCurrentDir()
   if(getcwd(buf, buflen)) {
     return std::string(buf);
   } else {
-    return A2STR::DOT_C;
+    return ".";
   }
 #endif // !__MINGW32__
 }
diff --git a/src/FtpConnection.cc b/src/FtpConnection.cc
index 30196f50..60b5e6c6 100644
--- a/src/FtpConnection.cc
+++ b/src/FtpConnection.cc
@@ -314,7 +314,7 @@ FtpConnection::findEndOfResponse
     if(p == std::string::npos) {
       return std::string::npos;
     }
-    p = buf.find(A2STR::CRLF, p+6);
+    p = buf.find("\r\n", p+6);
     if(p == std::string::npos) {
       return std::string::npos;
     } else {
@@ -322,7 +322,7 @@ FtpConnection::findEndOfResponse
     }
   } else {
     // single line response
-    std::string::size_type p = buf.find(A2STR::CRLF);    
+    std::string::size_type p = buf.find("\r\n");
     if(p == std::string::npos) {
       return std::string::npos;
     } else {
diff --git a/src/util.cc b/src/util.cc
index ea1b75c7..68bc7390 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -1371,7 +1371,7 @@ std::string applyDir(const std::string& dir, const std::string& relPath)
 std::string fixTaintedBasename(const std::string& src)
 {
   static std::string SLASH_REP = "%2F";
-  return escapePath(replace(src, A2STR::SLASH_C, SLASH_REP));
+  return escapePath(replace(src, "/", SLASH_REP));
 }
 
 void generateRandomKey(unsigned char* key)
diff --git a/test/ExceptionTest.cc b/test/ExceptionTest.cc
index fe1697f6..1a7c1065 100644
--- a/test/ExceptionTest.cc
+++ b/test/ExceptionTest.cc
@@ -38,7 +38,7 @@ void ExceptionTest::testStackTrace()
      ("Exception: [ExceptionTest.cc:34] errorCode=2 exception thrown\n"
       "  -> [ExceptionTest.cc:32] errorCode=2 cause2\n"
       "  -> [ExceptionTest.cc:31] errorCode=2 cause1\n"),
-     util::replace(e.stackTrace(), A2_TEST_DIR+A2STR::SLASH_C, ""));
+     util::replace(e.stackTrace(), std::string(A2_TEST_DIR)+"/", ""));
 }
 
 } // namespace aria2