diff --git a/src/AuthConfigFactory.cc b/src/AuthConfigFactory.cc
index c2448fdd..effd1ff4 100644
--- a/src/AuthConfigFactory.cc
+++ b/src/AuthConfigFactory.cc
@@ -47,9 +47,10 @@
 
 namespace aria2 {
 
-const std::string AuthConfigFactory::ANONYMOUS("anonymous");
-
-const std::string AuthConfigFactory::ARIA2USER_AT("ARIA2USER@");
+namespace {
+const std::string AUTH_DEFAULT_USER("anonymous");
+const std::string AUTH_DEFAULT_PASSWD("ARIA2USER@");
+} // namespace
 
 AuthConfigFactory::AuthConfigFactory() {}
 
@@ -160,8 +161,7 @@ AuthResolverHandle AuthConfigFactory::createFtpAuthResolver
   resolver->setUserDefinedAuthConfig
     (createAuthConfig(op->get(PREF_FTP_USER), op->get(PREF_FTP_PASSWD)));
   SharedHandle<AuthConfig> defaultAuthConfig
-    (new AuthConfig(AuthConfigFactory::ANONYMOUS,
-                    AuthConfigFactory::ARIA2USER_AT));
+    (new AuthConfig(AUTH_DEFAULT_USER, AUTH_DEFAULT_PASSWD));
   resolver->setDefaultAuthConfig(defaultAuthConfig);
   return resolver;
 }
diff --git a/src/AuthConfigFactory.h b/src/AuthConfigFactory.h
index 3ef2863d..abd8efb8 100644
--- a/src/AuthConfigFactory.h
+++ b/src/AuthConfigFactory.h
@@ -129,10 +129,6 @@ public:
   // given basicCred. Otherwise, insert given basicCred to
   // basicCreds_.
   void updateBasicCred(const SharedHandle<BasicCred>& basicCred);
-
-  static const std::string ANONYMOUS;
-
-  static const std::string ARIA2USER_AT;
 };
 
 typedef SharedHandle<AuthConfigFactory> AuthConfigFactoryHandle;