Getting "symbol ap_cache_cacheable_hdrs_out: referenced symbol not found" during loading mod_mem_cache.so at Apache httpd start-up

Issue

Getting the following error at Apache httpd start-up:

httpd.worker: Syntax error on line XXX of /opt/jboss-ews-2.1/etc/httpd/conf/httpd.conf: Cannot load /opt/jboss-ews-2.1/etc/httpd/modules/mod_mem_cache.so into server: ld.so.1: httpd.worker: fatal: relocation error: file /opt/jboss-ews-2.1/etc/httpd/modules/mod_mem_cache.so: symbol ap_cache_cacheable_hdrs_out: referenced symbol not found