Address Validate response error - usps.usps.USPSApiError: XML Syntax Error: Please check the XML request to see if it can be parsed.(B)

[nmogral]

The following address check "1400 Carpentier St Apt 326, San Leandro, CA 94577-3630" works fine but I get an error when "Apt" is replaced with a '#' sign.

address = Address(
name='Test',
address_1='1400 Carpentier St # 326',
city='San Leandro',
state='CA',
zipcode='94577-3630'
)
usps.usps.USPSApiError: XML Syntax Error: Please check the XML request to see if it can be parsed.(B)