A check is done on HAProxy version to be sure it is supported. Internally, by default, the macro 'no-htx' is set to "#". So in regtests, we can prefix http-use-htx option line with this macro to inhibit the HTX. Concretly, this line can be added in the HAProxy configuration: ${no-htx} option http-use-htx When the option --use-htx is used, the macro 'no-htx' is unset.