Issue #21866: ZipFile.close() no longer writes ZIP64 central directory
records if allowZip64 is false.
diff --git a/Lib/test/test_zipfile64.py b/Lib/test/test_zipfile64.py
index a6f3dca..a87baaa 100644
--- a/Lib/test/test_zipfile64.py
+++ b/Lib/test/test_zipfile64.py
@@ -99,7 +99,7 @@
     def testMoreThan64kFiles(self):
         # This test checks that more than 64k files can be added to an archive,
         # and that the resulting archive can be read properly by ZipFile
-        zipf = zipfile.ZipFile(TESTFN, mode="w")
+        zipf = zipfile.ZipFile(TESTFN, mode="w", allowZip64=True)
         zipf.debug = 100
         numfiles = (1 << 16) * 3/2
         for i in xrange(numfiles):
@@ -111,8 +111,43 @@
         self.assertEqual(len(zipf2.namelist()), numfiles)
         for i in xrange(numfiles):
             self.assertEqual(zipf2.read("foo%08d" % i), "%d" % (i**3 % 57))
+        zipf2.close()
+
+    def testMoreThan64kFilesAppend(self):
+        zipf = zipfile.ZipFile(TESTFN, mode="w", allowZip64=False)
+        zipf.debug = 100
+        numfiles = (1 << 16) - 1
+        for i in range(numfiles):
+            zipf.writestr("foo%08d" % i, "%d" % (i**3 % 57))
+        self.assertEqual(len(zipf.namelist()), numfiles)
+        with self.assertRaises(zipfile.LargeZipFile):
+            zipf.writestr("foo%08d" % numfiles, b'')
+        self.assertEqual(len(zipf.namelist()), numfiles)
         zipf.close()
 
+        zipf = zipfile.ZipFile(TESTFN, mode="a", allowZip64=False)
+        zipf.debug = 100
+        self.assertEqual(len(zipf.namelist()), numfiles)
+        with self.assertRaises(zipfile.LargeZipFile):
+            zipf.writestr("foo%08d" % numfiles, b'')
+        self.assertEqual(len(zipf.namelist()), numfiles)
+        zipf.close()
+
+        zipf = zipfile.ZipFile(TESTFN, mode="a", allowZip64=True)
+        zipf.debug = 100
+        self.assertEqual(len(zipf.namelist()), numfiles)
+        numfiles2 = (1 << 16) * 3//2
+        for i in range(numfiles, numfiles2):
+            zipf.writestr("foo%08d" % i, "%d" % (i**3 % 57))
+        self.assertEqual(len(zipf.namelist()), numfiles2)
+        zipf.close()
+
+        zipf2 = zipfile.ZipFile(TESTFN, mode="r")
+        self.assertEqual(len(zipf2.namelist()), numfiles2)
+        for i in range(numfiles2):
+            self.assertEqual(zipf2.read("foo%08d" % i), "%d" % (i**3 % 57))
+        zipf2.close()
+
     def tearDown(self):
         test_support.unlink(TESTFN)
         test_support.unlink(TESTFN2)