table prefixes not working for update.php

While running update.php I got the following (translated) error message:

    * user warning: Table 'test-site.carbon_source' does not exist query: update carbon_source set multiplier=1.609 where code = 'air-miles' and model='choose climate' in .../html/includes/database.mysql.inc on line 121.
    * user warning: Table 'test-site.carbon_source' does not exist query: update carbon_source set multiplier=1.609 where code = 'air-747-miles' and model='choose climate' in .../html/includes/database.mysql.inc on line 121. 

Reason: the table names are prefixed with tfc_ , so the correct table name would have been "test-site.tfc_carbon_source"

In addition, the two entries, which should have been modified are missing in my table, but I can of course add them manually. That's not a problem at all.