diff --git a/etc/README b/etc/README
index 80c4b3c..c4532bb 100644
--- a/etc/README
+++ b/etc/README
@@ -1,6 +1,9 @@
 > N.B. If you're interested in building Midipix using this script, please join the project's
 IRC channel #midipix on Freenode and ask for the address of the internal repositories.
 
+> N.B. If in doubt, consult the fault-tolerant & highly optimised 3D laser show-equipped
+usage screen w/ ./build.sh -h or a hungry lion may eat you alive.
+
 A Midipix distribution consists of the following:
 * the native Midipix toolchain, consisting of perk, gcc, its dependencies,
   and binutils,
diff --git a/etc/build.usage b/etc/build.usage
index 2150db1..ee7f249 100644
--- a/etc/build.usage
+++ b/etc/build.usage
@@ -42,6 +42,7 @@ usage: ./build.sh [-a nt32|nt64] [-b debug|release] [-C dir[,..]] [-D kind[,..]]
                           native_packages, native_runtime, native_toolchain, and/or native_tools.
 
         ${HOME}/midipix_build.vars, ${HOME}/.midipix_build.vars, and/or ../midipix_build.vars will be sourced if present.
+        If either of ${DEFAULT_GITROOT_HEAD} and/or ${DEFAULT_ZIPDIST_SIGN_GPG_KEY} are to be set, export(1) them there.
 
         Examples:
         ./build.sh -r coreutils