pt-table-usage fails to parse double parenthesis when a column have a function definition

While pt-table-usage is capable of parse correctly a column of the form: round(num), it get's trouble in presence of double parenthesis: round(sum(num))

Test case:
[percona@machine]$ cat a.txt
# Query_id: 16717677
select round(sum(num))
from db.tbl;

[percona@machine]$ ./pt-table-usage --id-attribute=Query_id a.txt
Error getting table usage: Column ident match failed at ./pt-table-usage line 3748, <> line 1.

[percona@machine]$ ./pt-table-usage --version
pt-table-usage 2.2.13

Verified also on previous version 2.2.5:
[percona@machine$ pt-table-usage --id-attribute=Query_id a.txt
Error getting table usage: Column ident match failed at /usr/bin/pt-table-usage line 3713, <> line 1.