diff --git a/test/zlib/test_zlib.rb b/test/zlib/test_zlib.rb
index b642fabc8e..4832bcf540 100644
--- a/test/zlib/test_zlib.rb
+++ b/test/zlib/test_zlib.rb
@@ -1,10 +1,15 @@
 require 'test/unit/testsuite'
 require 'test/unit/testcase'
 
-require 'zlib'
+begin
+  require 'zlib'
+rescue LoadError
+end
 
-class TestZlibGzipWriter < Test::Unit::TestCase
-  def test_new_nil # [ruby-dev:23228]
-    assert_raises(NoMethodError) { Zlib::GzipWriter.new(nil).close }
+if defined? Zlib
+  class TestZlibGzipWriter < Test::Unit::TestCase
+    def test_new_nil # [ruby-dev:23228]
+      assert_raises(NoMethodError) { Zlib::GzipWriter.new(nil).close }
+    end
   end
 end