[derefr]

Yeah, it doesn’t include it all the time. It’s an option, though, and one that the OP might have accidentally been using. (I think in relx there’s an explicit `include_src` flag you pass to enable it.) I was just justifying the presence of the option. It’s not always, or even usually necessary.

[kungfooguru]

Not a big deal but, it was actually a bug in relx that caused it to be included (accidentally copying the erts dir from the symlink/copy in the _build/<profile>/rel/<relname>/ dir instead of from the unpacked tarball generated by systools when doing the final assembly), not `include_src`, that option only applies to the Erlang applications and not the runtime.