Package: apache2-dev Version: 2.4.23-5 Severity: serious Looking at mod_ssl_openssl.h and the comment in #828330, I'd suggest the change below to add a dependency on libssl1.0-dev to apache2-dev.
This would prevent packages from build-depending (directly or indirectly) on both apache2-dev and the OpenSSL 1.1 libssl-dev. --- debian/control.old 2016-11-12 13:18:55.000000000 +0000 +++ debian/control 2016-11-12 13:30:56.000000000 +0000 @@ -121,7 +121,7 @@ Package: apache2-dev Architecture: any Depends: ${misc:Depends}, openssl, - libapr1-dev, libaprutil1-dev, debhelper (>= 9), ${perl:Depends} + libapr1-dev, libaprutil1-dev, debhelper (>= 9), ${perl:Depends}, libssl1.0-dev | libssl-dev (<< 1.1) Provides: dh-apache2 Description: Apache HTTP Server (development headers) The Apache HTTP Server Project's goal is to build a secure, efficient and