diff --git a/lib/bitclust/searcher.rb b/lib/bitclust/searcher.rb
index 8ce67cb..70af702 100644
--- a/lib/bitclust/searcher.rb
+++ b/lib/bitclust/searcher.rb
@@ -190,7 +190,7 @@ module BitClust
     end
 
     def default_dbpath
-      datadir = ::Config::CONFIG['datadir']
+      datadir = ::RbConfig::CONFIG['datadir']
       [ "#{datadir}/refe2", "#{datadir}/bitclust" ].each do |path|
         return path if MethodDatabase.datadir?(path)
       end
diff --git a/packer.rb b/packer.rb
index 4c8bc41..dff1609 100755
--- a/packer.rb
+++ b/packer.rb
@@ -8,8 +8,8 @@ ruby = nil
 begin
   require "rbconfig"
   ruby = File.join(
-    Config::CONFIG["bindir"],
-    Config::CONFIG["ruby_install_name"] + Config::CONFIG["EXEEXT"]
+    RbConfig::CONFIG["bindir"],
+    RbConfig::CONFIG["ruby_install_name"] + RbConfig::CONFIG["EXEEXT"]
   )
 rescue LoadError
   ruby = "ruby"
diff --git a/setup.rb b/setup.rb
index c0b6da7..112c47e 100644
--- a/setup.rb
+++ b/setup.rb
@@ -786,7 +786,7 @@ class ToplevelInstaller
     else
       require 'rbconfig'
     end
-    ::Config::CONFIG
+    ::RbConfig::CONFIG
   end
 
   def initialize(ardir_root, config)