diff --git a/common.mk b/common.mk
index c15104ae12..b05f1dab09 100644
--- a/common.mk
+++ b/common.mk
@@ -61,6 +61,7 @@ ENC_TRANS_D   = $(TIMESTAMPDIR)/.enc-trans.time
 RDOCOUT       = $(EXTOUT)/rdoc
 HTMLOUT       = $(EXTOUT)/html
 CAPIOUT       = doc/capi
+INSTALL_DOC_OPTS = --rdoc-output="$(RDOCOUT)" --html-output="$(HTMLOUT)"
 
 INITOBJS      = dmyext.$(OBJEXT) dmyenc.$(OBJEXT)
 NORMALMAINOBJ = main.$(OBJEXT)
@@ -352,7 +353,7 @@ $(ruby_pc): $(srcdir)/template/ruby.pc.in config.status
 install-all: docs pre-install-all do-install-all post-install-all
 pre-install-all:: all pre-install-local pre-install-ext pre-install-doc
 do-install-all: pre-install-all
-	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=all --rdoc-output="$(RDOCOUT)"
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=all $(INSTALL_DOC_OPTS)
 post-install-all:: post-install-local post-install-ext post-install-doc
 	@$(NULLCMD)
 
@@ -434,7 +435,7 @@ what-where-all: no-install-all
 no-install-all: pre-no-install-all dont-install-all post-no-install-all
 pre-no-install-all:: pre-no-install-local pre-no-install-ext pre-no-install-doc
 dont-install-all: $(PROGRAM)
-	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=all --rdoc-output="$(RDOCOUT)"
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=all $(INSTALL_DOC_OPTS)
 post-no-install-all:: post-no-install-local post-no-install-ext post-no-install-doc
 	@$(NULLCMD)
 
@@ -521,7 +522,7 @@ post-no-install-man::
 install-doc: rdoc pre-install-doc do-install-doc post-install-doc
 pre-install-doc:: install-prereq
 do-install-doc: $(PROGRAM) pre-install-doc
-	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc --rdoc-output="$(RDOCOUT)"
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc $(INSTALL_DOC_OPTS)
 post-install-doc::
 	@$(NULLCMD)
 
@@ -560,7 +561,7 @@ what-where-doc: no-install-doc
 no-install-doc: pre-no-install-doc dont-install-doc post-no-install-doc
 pre-no-install-doc:: install-prereq
 dont-install-doc:: $(PREP)
-	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc --rdoc-output="$(RDOCOUT)"
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc $(INSTALL_DOC_OPTS)
 post-no-install-doc::
 	@$(NULLCMD)
 
diff --git a/tool/rbinstall.rb b/tool/rbinstall.rb
index a3361e69a4..5687a688b3 100755
--- a/tool/rbinstall.rb
+++ b/tool/rbinstall.rb
@@ -42,6 +42,7 @@ def parse_args(argv = ARGV)
   $installed_list = nil
   $dryrun = false
   $rdocdir = nil
+  $htmldir = nil
   $data_mode = 0644
   $prog_mode = 0755
   $dir_mode = nil
@@ -80,6 +81,7 @@ def parse_args(argv = ARGV)
   end
   opt.on('--installed-list [FILENAME]') {|name| $installed_list = name}
   opt.on('--rdoc-output [DIR]') {|dir| $rdocdir = dir}
+  opt.on('--html-output [DIR]') {|dir| $htmldir = dir}
   opt.on('--cmd-type=TYPE', %w[cmd plain]) {|cmd| $cmdtype = (cmd unless cmd == 'plain')}
   opt.on('--[no-]strip') {|strip| $strip = strip}
 
@@ -134,6 +136,7 @@ def parse_args(argv = ARGV)
   end
 
   $rdocdir ||= $mflags.defined?('RDOCOUT')
+  $htmldir ||= $mflags.defined?('HTMLOUT')
 
   $dir_mode ||= $prog_mode | 0700
   $script_mode ||= $prog_mode
@@ -421,6 +424,12 @@ install?(:doc, :rdoc) do
     install_recursive($rdocdir, ridatadir, :mode => $data_mode)
   end
 end
+install?(:doc, :html) do
+  if $htmldir
+    prepare "html-docs", docdir
+    install_recursive($htmldir, docdir+"/html", :mode => $data_mode)
+  end
+end
 install?(:doc, :capi) do
   prepare "capi-docs", docdir
   install_recursive "doc/capi", docdir+"/capi", :mode => $data_mode