diff --git a/build_library/base_image_util.sh b/build_library/base_image_util.sh
index d33c81fcea..d3cc554bfb 100755
--- a/build_library/base_image_util.sh
+++ b/build_library/base_image_util.sh
@@ -143,7 +143,7 @@ create_base_image() {
 
   # First thing first, install baselayout with USE=build to create a
   # working directory tree. Don't use binpkgs due to the use flag change.
-  sudo -E USE=build ${EMERGE_BOARD_CMD} --root="${root_fs_dir}" \
+  sudo -E USE=build "emerge-${BOARD}" --root="${root_fs_dir}" \
       --usepkg=n --buildpkg=n --oneshot --quiet --nodeps sys-apps/baselayout
 
   # We need to install libc manually from the cross toolchain.
diff --git a/build_library/build_image_util.sh b/build_library/build_image_util.sh
index eb84a2e05d..1adc1055ec 100755
--- a/build_library/build_image_util.sh
+++ b/build_library/build_image_util.sh
@@ -20,15 +20,6 @@ BUILD_DIR="${FLAGS_output_root}/${BOARD}/${IMAGE_SUBDIR}"
 OUTSIDE_OUTPUT_DIR="../build/images/${BOARD}/${IMAGE_SUBDIR}"
 IMAGES_TO_BUILD=
 
-EMERGE_BOARD_CMD="$GCLIENT_ROOT/chromite/bin/parallel_emerge"
-EMERGE_BOARD_CMD="$EMERGE_BOARD_CMD --board=$BOARD"
-
-export INSTALL_MASK="${DEFAULT_INSTALL_MASK}"
-
-if [[ $FLAGS_jobs -ne -1 ]]; then
-  EMERGE_JOBS="--jobs=$FLAGS_jobs"
-fi
-
 # Populates list of IMAGES_TO_BUILD from args passed in.
 # Arguments should be the shortnames of images we want to build.
 get_images_to_build() {
@@ -140,6 +131,14 @@ generate_au_zip () {
 # Arguments to this command are passed as addition options/arguments
 # to the basic emerge command.
 emerge_to_image() {
-  sudo -E ${EMERGE_BOARD_CMD} --root-deps=rdeps --usepkgonly -v \
-    "$@" ${EMERGE_JOBS}
+  local mask="${INSTALL_MASK:-$(portageq-$BOARD envvar PROD_INSTALL_MASK)}"
+  test -n "$mask" || die "PROD_INSTALL_MASK not defined"
+  local emerge_cmd="$GCLIENT_ROOT/chromite/bin/parallel_emerge"
+  emerge_cmd+=" --board=$BOARD --root-deps=rdeps --usepkgonly -v"
+
+  if [[ $FLAGS_jobs -ne -1 ]]; then
+    emerge_cmd+=" --jobs=$FLAGS_jobs"
+  fi
+
+  sudo -E INSTALL_MASK="$mask" ${emerge_cmd} "$@"
 }
diff --git a/common.sh b/common.sh
index e398350011..aed9992740 100644
--- a/common.sh
+++ b/common.sh
@@ -413,49 +413,6 @@ COREOS_DEVELOPER_IMAGE_NAME=${CHROMEOS_DEVELOPER_IMAGE_NAME}
 COREOS_PRODUCTION_IMAGE_NAME="coreos_production_image.bin"
 COREOS_RECOVERY_IMAGE_NAME=${CHROMEOS_RECOVERY_IMAGE_NAME}
 
-# Install make for portage ebuilds.  Used by build_image and gmergefs.
-# TODO: Is /usr/local/autotest-chrome still used by anyone?
-COMMON_INSTALL_MASK="
-  *.a
-  *.la
-  *.h
-  *.hpp
-  /etc/init.d
-  /etc/runlevels
-  /firmware
-  /lib/rc
-  /usr/bin/Xnest
-  /usr/bin/Xvfb
-  /usr/lib/debug
-  /usr/lib/gcc
-  /usr/lib*/pkgconfig
-  /usr/lib/systemd/system/local-fs.target.wants
-  /usr/local/autotest-chrome
-  /usr/man
-  /usr/share/aclocal
-  /usr/share/doc
-  /usr/share/gettext
-  /usr/share/gtk-2.0
-  /usr/share/gtk-doc
-  /usr/share/info
-  /usr/share/man
-  /usr/share/openrc
-  /usr/share/pkgconfig
-  /usr/share/profiling
-  /usr/share/readline
-  /usr/src
-  "
-
-# Mask for base, dev, and test images (build_image, build_image --test)
-DEFAULT_INSTALL_MASK="
-  ${COMMON_INSTALL_MASK}
-  /usr/local/autotest
-  /lib/modules/*/kernel/drivers/input/misc/uinput.ko
-  /lib/modules/*/build
-  /lib/modules/*/source
-  test_*.ko
-  "
-
 # -----------------------------------------------------------------------------
 # Functions