diff --git a/test/zlib/test_zlib.rb b/test/zlib/test_zlib.rb
index 502ccce..ae4adc2 100644
--- a/test/zlib/test_zlib.rb
+++ b/test/zlib/test_zlib.rb
@@ -801,7 +801,8 @@ def test_path_tmpfile
         gz.write "hi"
         gz.close
 
-        File.open(Dir.mktmpdir, File::RDWR | File::TMPFILE) do |io|
+        tmpdir = Dir.mktmpdir("zlib_file_tmpfile")
+        File.open(tmpdir, File::RDWR | File::TMPFILE) do |io|
           io.write sio.string
           io.rewind
 
@@ -825,6 +826,8 @@ def test_path_tmpfile
         omit 'O_TMPFILE not supported (EISDIR)'
       rescue Errno::EOPNOTSUPP
         omit 'O_TMPFILE not supported (EOPNOTSUPP)'
+      ensure
+        Dir.rmdir(tmpdir) if tmpdir
       end
     end
   end