diff --git a/lib/cgi/session.rb b/lib/cgi/session.rb
index aab6086..6d93566 100644
--- a/lib/cgi/session.rb
+++ b/lib/cgi/session.rb
@@ -210,15 +210,19 @@ def create_new_id
     # suffix:: the prefix to add to the session id when generating
     #          the filename for this session's FileStore file.
     #          Defaults to the empty string.
+    # digest:: the digest algorithm to hash the session id when
+    #          generating the filename for this session's FileStore
+    #          file.  Defaults to "MD5".
     def new_store_file(option={}) # :nodoc:
       dir = option['tmpdir'] || Dir::tmpdir
       prefix = option['prefix']
       suffix = option['suffix']
-      require 'digest/md5'
-      md5 = Digest::MD5.hexdigest(session_id)[0,16]
+      algorithm = option['digest'] || 'MD5'
+      require 'digest'
+      digest = Digest(algorithm).hexdigest(session_id)[0,16]
       path = dir+"/"
       path << prefix if prefix
-      path << md5
+      path << digest
       path << suffix if suffix
       if File::exist? path
         hash = nil
@@ -410,6 +414,9 @@ class FileStore
       # suffix:: the prefix to add to the session id when generating
       #          the filename for this session's FileStore file.
       #          Defaults to the empty string.
+      # digest:: the digest algorithm to hash the session id when
+      #          generating the filename for this session's FileStore
+      #          file.  Defaults to "MD5".
       #
       # This session's FileStore file will be created if it does
       # not exist, or opened if it does.
diff --git a/test/cgi/test_cgi_session.rb b/test/cgi/test_cgi_session.rb
index 32b907d..722c471 100644
--- a/test/cgi/test_cgi_session.rb
+++ b/test/cgi/test_cgi_session.rb
@@ -55,8 +55,8 @@ def test_cgi_session_filestore
     assert_equal(value1,session["key1"])
     assert_equal(value2,session["key2"])
     session.close
-
   end
+
   def test_cgi_session_pstore
     update_env(
       'REQUEST_METHOD'  => 'GET',
@@ -92,6 +92,7 @@ def test_cgi_session_pstore
     assert_equal(value2,session["key2"])
     session.close
   end if defined?(::PStore)
+
   def test_cgi_session_specify_session_id
     update_env(
       'REQUEST_METHOD'  => 'GET',
@@ -130,6 +131,7 @@ def test_cgi_session_specify_session_id
     assert_equal("foo",session.session_id)
     session.close
   end
+
   def test_cgi_session_specify_session_key
     update_env(
       'REQUEST_METHOD'  => 'GET',
@@ -166,4 +168,23 @@ def test_cgi_session_specify_session_key
     assert_equal(value2,session["key2"])
     session.close
   end
+
+  def test_cgi_session_filestore_digest
+    session_id = "banana"
+    path_md5 = session_file_store_path("tmpdir"=>@session_dir, "session_id"=>session_id)
+    assert_equal path_md5, session_file_store_path("tmpdir"=>@session_dir, "session_id"=>session_id)
+    path_sha512 = session_file_store_path("tmpdir"=>@session_dir, "session_id"=>session_id, "digest"=>"SHA512")
+    assert_not_equal path_sha512, path_md5
+  end
+
+  private
+
+  def session_file_store_path(options)
+    cgi = Object.new
+    session = CGI::Session.new(cgi, options)
+    session.delete
+    dbman = session.instance_variable_get(:@dbman)
+    assert_kind_of(CGI::Session::FileStore, dbman)
+    dbman.instance_variable_get(:@path)
+  end
 end