diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -750,6 +750,61 @@
 
 Test""")
 
+    def test_long_run_with_semi_header_splitter(self):
+        # Issue 11492
+        eq = self.ndiffAssertEqual
+        msg = Message()
+        msg['From'] = 'test@dom.ain'
+        msg['References'] = SPACE.join(['<food@dom.ain>'] * 10) + '; abc'
+        msg.set_payload('Test')
+        sfp = StringIO()
+        g = Generator(sfp)
+        g.flatten(msg)
+        eq(sfp.getvalue(), """\
+From: test@dom.ain
+References: <foo@dom.ain> <foo@dom.ain> <foo@dom.ain> <foo@dom.ain>
+ <foo@dom.ain> <foo@dom.ain> <foo@dom.ain> <foo@dom.ain> <foo@dom.ain>
+ <foo@dom.ain>;
+ abc
+
+Test""")
+
+    def test_long_header_with_whitespace_runs(self):
+        # Issue XXXXX
+        eq = self.ndiffAssertEqual
+        msg = Message()
+        msg['From'] = 'test@dom.ain'
+        msg['References'] = SPACE.join(['<foo@dom.ain>  '] * 10)
+        msg.set_payload('Test')
+        sfp = StringIO()
+        g = Generator(sfp)
+        g.flatten(msg)
+        eq(sfp.getvalue(), """\
+From: test@dom.ain
+References: <foo@dom.ain>   <foo@dom.ain>   <foo@dom.ain>   <foo@dom.ain>
+    <foo@dom.ain>   <foo@dom.ain>   <foo@dom.ain>   <foo@dom.ain>
+    <foo@dom.ain>   <foo@dom.ain>
+
+Test""")
+
+    def test_splitter_split_on_punctuation_only_if_fws(self):
+        # Issue XXXXX
+        eq = self.ndiffAssertEqual
+        msg = Message()
+        msg['From'] = 'test@dom.ain'
+        msg['References'] = ('thisverylongheaderhas;semicolons;and,commas,but'
+            'they;arenotlegal;fold,points')
+        msg.set_payload('Test')
+        sfp = StringIO()
+        g = Generator(sfp)
+        g.flatten(msg)
+        eq(sfp.getvalue(), """\
+From: test@dom.ain
+References:
+ thisverylongheaderhas;semicolons;and,commas,butthey;arenotlegal;fold,points
+
+Test""")
+
     def test_no_split_long_header(self):
         eq = self.ndiffAssertEqual
         hstr = 'References: ' + 'x' * 80