AWS WAF URI regex don't match

Hi, I created a Web ACL with one rule to allow traffic only on some enpoint, and the default ACL action is to block requests that don't match the rule.

## Rule
Field to Match: URI Path
Regular Expression: /(account|category|post)/ 
Action: ALLOW

##  Default web ACL action for requests that don't match any rules
Action: BLOCK

The problem is that the rule match only path with two or more segments, but don't match path with 1 segment.

http://api.example.com/account/foo/bar     => MATCH - ALLOW
http://api.example.com/account/foo?bar=baz => MATCH - ALLOW
http://api.example.com/account/foo         => MATCH - ALLOW

http://api.example.com/account             => DON'T MATCH - BLOCK
http://api.example.com/account?foo=bar     => DON'T MATCH - BLOCK

What's wrong? I would like the rule matches also path with 1 segment. Thanks in advance