You must upgrade your ACS compiler to use ACSUtils because the official ACC 1.55 release can't compile files with more than 256 functions.

Upgrade to one of the following compilers:

• ACC 1.56 Beta: DOWNLOAD. This archive also includes the latest Zandronum zcommon from https://github.com/Korshun/zcommon.
• BCC
• GDCC

1. Download the latest release.
2. Add acsutils.acs to your project.
3. Include acsutils.acs after zcommon.acs:

#include "zcommon.acs"
#include "acsutils.acs"

1. Copy decorate/changeflag.txt to your decorate and #include it to make ChangeFlag and ChangeActorFlag work.
2. Copy cvarinfo.acsutils to your project root to allow the server to hide ACSUtils errors using the acsutils_noerrors cvar.