There is an XS-Testsuite field in the debian/control file. As of dpkg 1.17.10, the XS- prefix is no longer necessary. dpkg now recognizes this field and handles it correctly. As of dpkg 1.17.11 the field is automatically added by dpkg-source with the value "autopkgtest" if there is a non-empty debian/tests/control file present. Consider either removing the XS- prefix for this field or removing the field altogether if it contains just the "autopkgtest" value.