diff --git a/Lib/Cookie.py b/Lib/Cookie.py
index 0b15531..b1704d9 100644
--- a/Lib/Cookie.py
+++ b/Lib/Cookie.py
@@ -528,12 +528,13 @@
 # result, the parsing rules here are less strict.
 #
 
-_LegalCharsPatt  = r"[\w\d!#%&'~_`><@,:/\$\*\+\-\.\^\|\)\(\?\}\{\=]"
+_LegalKeyChars  = r"\w\d!#%&'~_`><@,:/\$\*\+\-\.\^\|\)\(\?\}\{\="
+_LegalValueChars = _LegalKeyChars + r"\[\]"
 _CookiePattern = re.compile(
     r"(?x)"                       # This is a Verbose pattern
     r"\s*"                        # Optional whitespace at start of cookie
     r"(?P<key>"                   # Start of group 'key'
-    ""+ _LegalCharsPatt +"+?"     # Any word of at least one letter, nongreedy
+    "["+ _LegalKeyChars +"]+?"     # Any word of at least one letter, nongreedy
     r")"                          # End of group 'key'
     r"("                          # Optional group: there may not be a value.
     r"\s*=\s*"                    # Equal Sign
@@ -542,7 +543,7 @@
     r"|"                            # or
     r"\w{3},\s[\s\w\d-]{9,11}\s[\d:]{8}\sGMT" # Special case for "expires" attr
     r"|"                            # or
-    ""+ _LegalCharsPatt +"*"        # Any word or empty string
+    "["+ _LegalValueChars +"]*"        # Any word or empty string
     r")"                          # End of group 'val'
     r")?"                         # End of optional value group
     r"\s*"                        # Any number of spaces.
diff --git a/Lib/test/test_cookie.py b/Lib/test/test_cookie.py
index 36cd52e..4041901 100644
--- a/Lib/test/test_cookie.py
+++ b/Lib/test/test_cookie.py
@@ -27,6 +27,20 @@
               'dict': {'keebler' : 'E=mc2'},
               'repr': "<SimpleCookie: keebler='E=mc2'>",
               'output': 'Set-Cookie: keebler=E=mc2',
+            },
+
+            # issue22931 - Adding '[' and ']' as valid characters in cookie
+            # values as defined in RFC 6265
+            {
+                'data': 'a=b; c=[; d=r; f=h',
+                'dict': {'a':'b', 'c':'[', 'd':'r', 'f':'h'},
+                'repr': "<SimpleCookie: a='b' c='[' d='r' f='h'>",
+                'output': '\n'.join((
+                    'Set-Cookie: a=b',
+                    'Set-Cookie: c=[',
+                    'Set-Cookie: d=r',
+                    'Set-Cookie: f=h'
+                ))
             }
         ]