Unable to map file name (containing uppercase & digit) to domain name

In documentation of under [Mapping of file paths to domain names](http://h5serv.readthedocs.io/en/latest/DomainOps/index.html#mapping-of-file-paths-to-domain-names) it says

> For path names that include non-alphanumeric charters, replace any such characters with the string ‘%XX’ where XX is the hexidecimal value of the character.

I assumed that numeric characters in a filename are valid.

- When I tried to map **Filename2017_100.h5** with my domain to **filename2017_100.mydomain**, it gave me 500 response.
- When I removed numeric value from file name like **filename_test.h5**, it successfully mapped to **filename_test.mydomain**.

Not sure If I am missing something else. Is there a way to map domain name with a filename containing upper case and digit?