diff -r 2f0716009132 Lib/test/test_gzip.py
--- a/Lib/test/test_gzip.py	Tue Jul 12 18:24:25 2016 -0400
+++ b/Lib/test/test_gzip.py	Fri Jul 15 22:26:57 2016 +0300
@@ -619,6 +619,23 @@
         with gzip.open(self.filename, "rt", newline="\r") as f:
             self.assertEqual(f.readlines(), [uncompressed])
 
+    def test_compress_level(self):
+        # Test the compress level header, trying all the options.
+        uncompressed = data1 * 50
+        expected_xfl = [b'\x00']*10
+        expected_xfl[1] = b'\x04'
+        expected_xfl[9] = b'\x02'
+
+        for cl in range(10):
+            with gzip.open(self.filename, "w", compresslevel=cl) as f:
+                f.write(uncompressed)
+            with open(self.filename, "rb") as f:
+                f.seek(8)
+                xfl_byte = f.read(1)
+            print(cl, xfl_byte, expected_xfl[cl])
+            self.assertEqual(xfl_byte, expected_xfl[cl])
+
+
 def test_main(verbose=None):
     support.run_unittest(TestGzip, TestOpen)