diff --git a/test/socket/test_unix.rb b/test/socket/test_unix.rb
new file mode 100644
index 0000000000..1314fca1f8
--- /dev/null
+++ b/test/socket/test_unix.rb
@@ -0,0 +1,28 @@
+begin
+  require "socket"
+  require "test/unit"
+rescue LoadError
+end
+
+class TestUNIXSocket < Test::Unit::TestCase
+  def test_fd_passing
+    r1, w = IO.pipe
+    s1, s2 = UNIXSocket.pair
+    begin
+      s1.send_io r1
+    rescue NotImplementedError
+      s1.close
+      assert_raise(NotImplementedError) { s2.recv_io }
+      return
+    end
+    r2 = s2.recv_io
+    assert_equal(r1.stat.ino, r2.stat.ino)
+    assert_not_equal(r1.fileno, r2.fileno)
+  ensure
+    s1.close if s1
+    s2.close if s2
+    r1.close if r1
+    r2.close if r2
+    w.close if w
+  end
+end if defined?(UNIXSocket)