diff --git a/Lib/decimal.py b/Lib/decimal.py
index 04bf5c2..19cc50f 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -3665,6 +3665,8 @@
         if self._is_special:
             sign = _format_sign(self._sign, spec)
             body = str(self.copy_abs())
+            if spec['type'] == '%':
+                body += '%'
             return _format_align(sign, body, spec)
 
         # a type of None defaults to 'g' or 'G', depending on context
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 0902278..610a696 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -823,6 +823,11 @@
 
             # issue 6850
             ('a=-7.0', '0.12345', 'aaaa0.1'),
+
+            # issue 22090
+            ('<^+15.20%', 'inf', '<<+Infinity%<<<'),
+            ('\x07>,%', 'sNaN1234567', 'sNaN1234567%'),
+            ('=10.10%', 'NaN123', '   NaN123%'),
             ]
         for fmt, d, result in test_values:
             self.assertEqual(format(Decimal(d), fmt), result)