diff --git a/Lib/email/_policybase.py b/Lib/email/_policybase.py
index c0d98a4f5429357..7326d3a2b1671ea 100644
--- a/Lib/email/_policybase.py
+++ b/Lib/email/_policybase.py
@@ -357,8 +357,12 @@ def _fold(self, name, value, sanitize):
             # Assume it is a Header-like object.
             h = value
         if h is not None:
-            parts.append(h.encode(linesep=self.linesep,
-                                  maxlinelen=self.max_line_length))
+            # The Header class interprets a value of None for maxlinelen as the
+            # default value of 78, as recommended by RFC 2822.
+            maxlinelen = 0
+            if self.max_line_length is not None:
+                maxlinelen = self.max_line_length
+            parts.append(h.encode(linesep=self.linesep, maxlinelen=maxlinelen))
         parts.append(self.linesep)
         return ''.join(parts)
 
diff --git a/Lib/test/test_email/test_generator.py b/Lib/test/test_email/test_generator.py
index b1cbce26d5c1fb9..226c5f98c4039cf 100644
--- a/Lib/test/test_email/test_generator.py
+++ b/Lib/test/test_email/test_generator.py
@@ -162,6 +162,13 @@ def test_set_mangle_from_via_policy(self):
                 g.flatten(msg)
                 self.assertEqual(s.getvalue(), self.typ(expected))
 
+    def test_compat32_max_line_length_does_not_fold_when_none(self):
+        msg = self.msgmaker(self.typ(self.refold_long_expected[0]))
+        s = self.ioclass()
+        g = self.genclass(s, policy=policy.compat32.clone(max_line_length=None))
+        g.flatten(msg)
+        self.assertEqual(s.getvalue(), self.typ(self.refold_long_expected[0]))
+
 
 class TestGenerator(TestGeneratorBase, TestEmailBase):