Module compiles, but ejabberd_config:get_global_option is undefined?

Hi everybody!

I am new to both Erlang as well as ejabberd module programming, so although I am searching and testing for some hours now, I might just not be asking the correct questions to google - if so: Sorry for that! ;)
The problem I have is that the module I am playing around with is using a call to:

ejabberd_config:get_global_option({access, Rule, global})

Everything compiles well, but I get an error in ejabberd.log, reading:
[...] @ejabberd_hooks:run_fold1:356 {undef,[{ejabberd_config,get_global_option, [...]

I have a similar problem before with the ?INFO_MSG makro, where it turned out that I needed to add the "-DLAGER" flag to my comilation command. However, for this specific case, I could not find a hint yet.

My compilation command reads:
erlc -DLAGER=true -I [...]/ejabberd/include/ -pa [...]/ejabberd/ebin/ myModule.erl

The headers included are:

Is it possible that the problem is that I am compiling against the headers only instead of against the complete source?

Any hint would be appreciated!

Thanks in advance,
volle