Unused classes gets compiled into swf

Question

I am building a swc [MY.swc] component with compc. It is suppose to contain base functionality for MY.swf
I need to include another (third party) swc [OTHER.swc] into my own swc. This other swc has a reference to mx.core.mx_internal and I suspect that it is this reference that in the end, when I compile MY.swf, results in that all mx classes (mx.*) and all spark classes (spark.*) is included in MY.swf (seen when decompiling)
The difference in size between MY.swf with/without OTHER.swc is ~180kB.
The only difference (when decompiling) MY.swc with/without OTHER.swc is that the first has a reference to mx.core.mx_internal
Here is the compc part from my ANT task:
<compc output="MY.swc">
<include-sources dir="${project.root}/${SRC_ROOT}" includes="*" />
<library-path dir="${project.root}/${LIBS_DIR}" includes="*" />
</compc>
Do you know if there is a problem with compiling a swc into another swc?
Any other ideas why all mx and spark classes are included?
Thanks!

Answer 1

I solved my own problem:
Needed to set append flag (in library-path) to false when building MY.swf
<compiler.library-path dir="${project.root}" append="false">
  <include name="${LIBS_DIR}" />
</compiler.library-path>
Have not yet figured out exacly why, but it resulted in that the unused classes were not compiled.