diff --git a/ChangeLog b/ChangeLog
index 784c174ff2..218f016eb7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+Sun May 24 00:52:54 2009  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
+
+	* configure.in ($ridir): new configuration. [ruby-core:23520].
+	  c.f. [ruby-core:23519].
+
+	  (--with-ridir): new configure option.
+
+	* tool/instruby.rb (:doc, :rdoc): uses $ridir instead of
+	  a fixed path.
+
+	* lib/rdoc/ri/paths.rb: follows $ridir.
+
+	* Makefile.in: removes RIDATADIR which is no longer used.
+
+	* bcc32/Makefile.sub: generates the 'ridir' entry for RbConfig.
+	  removes RIDATADIR which is no longer used.
+
+	* win32/Makefile.sub: ditto.
+
 Sat May 23 23:52:33 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* string.c (rb_str_each_char): return original string.
diff --git a/Makefile.in b/Makefile.in
index 167be6ec4c..e80d312f63 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -36,7 +36,6 @@ TESTS =
 RDOCTARGET = @RDOCTARGET@
 
 EXTOUT = @EXTOUT@
-RIDATADIR = $(DESTDIR)$(datadir)/ri/$(MAJOR).$(MINOR)/system
 arch_hdrdir = $(EXTOUT)/include/$(arch)
 VPATH = $(arch_hdrdir)/ruby:$(hdrdir)/ruby:$(srcdir):$(srcdir)/enc:$(srcdir)/missing
 
diff --git a/bcc32/Makefile.sub b/bcc32/Makefile.sub
index 15e9669060..834e8a5870 100644
--- a/bcc32/Makefile.sub
+++ b/bcc32/Makefile.sub
@@ -114,9 +114,6 @@ datadir = $(prefix)/share
 !ifndef EXTOUT
 EXTOUT = .ext
 !endif
-!ifndef RIDATADIR
-RIDATADIR = $(DESTDIR)$(datadir)/ri/$(MAJOR).$(MINOR)/system
-!endif
 !ifndef TESTUI
 TESTUI = console
 !endif
@@ -397,6 +394,7 @@ s,@includedir@,$${prefix}/include,;t t
 s,@oldincludedir@,/usr/include,;t t
 s,@infodir@,$${prefix}/info,;t t
 s,@mandir@,$${prefix}/man,;t t
+s,@ridir@,$${prefix}/share/ri,;t t
 s,@build@,$(CPU)-pc-$(OS),;t t
 s,@build_alias@,$(CPU)-$(OS),;t t
 s,@build_cpu@,$(CPU),;t t
diff --git a/configure.in b/configure.in
index 71614f975b..f03dbfe309 100644
--- a/configure.in
+++ b/configure.in
@@ -2292,11 +2292,19 @@ esac
 
 rubylibprefix='${libdir}/${RUBY_BASE_NAME}'
 AC_ARG_WITH(rubylibprefix,
-	    AS_HELP_STRING([--with-rubylibprefix=DIR], [prefix for ruby libraries [[LIBDIR/RUBY_INSTALL_NAME]]]),
+	    AS_HELP_STRING([--with-rubylibprefix=DIR], [prefix for ruby libraries [[LIBDIR/RUBY_BASE_NAME]]]),
 	    [rubylibprefix=$withval])
 RUBY_LIB_PREFIX=`eval echo \\"${rubylibprefix}\\"`
 AC_SUBST(rubylibprefix)
 
+RI_BASE_NAME=`echo ${RUBY_BASE_NAME} | sed 's/ruby/ri/'`
+ridir='${DATAROOTDIR}/${RI_BASE_NAME}'
+AC_ARG_WITH(ridir,
+	    AS_HELP_STRING([--with-ridir=DIR], [ri documentation [[DATAROOTDIR/ri]]]),
+	    [ridir=$withval])
+RIDIR=`eval echo \\"${ridir}\\"`
+AC_SUBST(ridir)
+
 AC_ARG_WITH(ruby-version,
 	    AS_HELP_STRING([--with-ruby-version=STR], [ruby version string for version specific directories [[full]] (full|minor|STR)]),
             [ruby_version=$withval],
diff --git a/lib/rdoc/ri/paths.rb b/lib/rdoc/ri/paths.rb
index 11bbf4573f..bce71b46f0 100644
--- a/lib/rdoc/ri/paths.rb
+++ b/lib/rdoc/ri/paths.rb
@@ -28,14 +28,25 @@ module RDoc::RI::Paths
 
   VERSION = RbConfig::CONFIG['ruby_version']
 
-  if m = /ruby/.match(RbConfig::CONFIG['RUBY_INSTALL_NAME'])
-    m = [m.pre_match, m.post_match]
+  if VERSION > '1.9.1'
+    if m = /ruby/.match(RbConfig::CONFIG['RUBY_INSTALL_NAME'])
+      m = [m.pre_match, m.post_match]
+    else
+      m = [""] * 2
+    end
+    ri = "#{m[0]}ri#{m[1]}"
+    rdoc = "#{m[0]}rdoc#{m[1]}"
+    base    = File.join(RbConfig::CONFIG['datadir'], ri, VERSION)
   else
-    m = [""] * 2
+    if m = /ruby/.match(RbConfig::CONFIG['RUBY_BASE_NAME'])
+      m = [m.pre_match, m.post_match]
+    else
+      m = [""] * 2
+    end
+    ri = "#{m[0]}ri#{m[1]}"
+    rdoc = "#{m[0]}rdoc#{m[1]}"
+    base = File.join(RbConfig::CONFIG['ridir'], VERSION)
   end
-  ri = "#{m[0]}ri#{m[1]}"
-  rdoc = "#{m[0]}rdoc#{m[1]}"
-  base    = File.join(RbConfig::CONFIG['datadir'], ri, VERSION)
   SYSDIR  = File.join(base, "system")
   SITEDIR = File.join(base, "site")
   HOMEDIR = (File.expand_path("~/.#{rdoc}") rescue nil)
diff --git a/tool/instruby.rb b/tool/instruby.rb
index 601c23675a..852a06d0f0 100755
--- a/tool/instruby.rb
+++ b/tool/instruby.rb
@@ -364,7 +364,7 @@ end
 
 install?(:doc, :rdoc) do
   if $rdocdir
-    ridatadir = File.join(CONFIG['datadir'], "ri", CONFIG['ruby_version'], "system")
+    ridatadir = File.join(CONFIG['ridir'], CONFIG['ruby_version'], "system")
     prepare "rdoc", ridatadir
     install_recursive($rdocdir, ridatadir, :mode => $data_mode)
   end
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index c9b245508d..a85ea4a139 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -140,9 +140,6 @@ datadir = $(prefix)/share
 !ifndef EXTOUT
 EXTOUT = .ext
 !endif
-!ifndef RIDATADIR
-RIDATADIR = $(DESTDIR)$(datadir)/ri/$(MAJOR).$(MINOR)/system
-!endif
 !ifndef TESTUI
 TESTUI = console
 !endif
@@ -595,6 +592,7 @@ s,@includedir@,$${prefix}/include,;t t
 s,@oldincludedir@,/usr/include,;t t
 s,@infodir@,$${prefix}/info,;t t
 s,@mandir@,$${prefix}/man,;t t
+s,@ridir@,$${prefix}/share/ri,;t t
 s,@build@,$(CPU)-pc-$(PLATFORM),;t t
 s,@build_alias@,$(CPU)-$(PLATFORM),;t t
 s,@build_cpu@,$(CPU),;t t