diff --git a/profiles/make.defaults b/profiles/make.defaults
new file mode 100644
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--- /dev/null
+++ b/profiles/make.defaults
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+# Copyright 1999-2020 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+#
+# System-wide defaults for the Portage system
+# See portage(5) manpage
+
+# Env vars to expand into USE vars.
+USE_EXPAND="GEOIDS_DATASETS GRAVITY_MODELS MAGNETIC_MODELS PRECISION"
+