Importing individual contacts with "For Duplicate Contacts: Update" empty fields in the CSV file does not update database fields to empty value

For example:

• address fields in database before import:
  Street Address: 81 Irishtown Road
  Supplemental Address 1: Bricklane
  Supplemental Address 2: Ringsend
  City: Dublin
  Postal Code Suffix:
  Postal Code: 4
• address fields in CSV file:
  Street Address: 18 Main Street
  Supplemental Address 1: Blackrock
  Supplemental Address 2:
  City: Dublin
  Postal Code Suffix:
  Postal Code:

• fields in database after import:
  Street Address: 18 Main Street
  Supplemental Address 1: Blackrock
  Supplemental Address 2: Ringsend
  City: Dublin
  Postal Code Suffix:
  Postal Code: 4

the resulting address is incorrect.