I have narrowed it down to the src/include/httpd.h file no longer including a static string of the Apache/mods version. This causes Makefile.PL to fail with a message: Apache Version 1.3.0 required, aborting... OUCH! This causes a failure in the make and thus mod_perl does not compile. Since the define for SERVER_VERSION/SERVER_BASEVERSION is based on previous definitions of $defines may I point you to this define for a fix? (From source code httpd.h) /* Numeric release version identifier: MMNNFFRBB: major minor fix final beta * Always increases along the same track as the source branch. * For example, Apache 1.4.2 would be '10402100', 2.5b7 would be '20500007'. */ #define APACHE_RELEASE 10314100 (end snip) I was able to compile a version by adding a line to Makefile.PL in the httpd_version sub, that forces it to find the right version (no I will not provide it, it was a ugly hack) (geek code: mod_perl-->+++, perl-->+++) Given enough time I could provide a fix but I figured you might be able to do so MUCH faster than me at this point. Given the nature of the problem - this might affect other modules written for Apache as well.