When creating automated tests for web applications, one major part is filling and submitting web forms. Filling out forms automatically is challenging, as form fields would typically be subject to specific constraints that prevent entry of invalid data. Modern test generators, such as the recently proposed Black Ostrich scanner, are already capable of identifying expected patterns for form values and solve them, using instance generators for regular expressions and/or string constraint solvers. String solvers, however, are limited to, well, strings.