diff --git a/etc/portage/package.env/firefox b/etc/portage/package.env/firefox
new file mode 100644
index 0000000..e67bb4c
--- /dev/null
+++ b/etc/portage/package.env/firefox
@@ -0,0 +1 @@
+www-client/firefox rust-makeopts.conf
diff --git a/etc/portage/package.env/gentoo-kernel b/etc/portage/package.env/gentoo-kernel
new file mode 100644
index 0000000..7a79e3a
--- /dev/null
+++ b/etc/portage/package.env/gentoo-kernel
@@ -0,0 +1 @@
+sys-kernel/gentoo-kernel enable-ccache.conf
diff --git a/etc/portage/package.env/rust b/etc/portage/package.env/rust
new file mode 100644
index 0000000..f3c66cc
--- /dev/null
+++ b/etc/portage/package.env/rust
@@ -0,0 +1 @@
+dev-lang/rust rust-makeopts.conf