diff --git a/build_image b/build_image
index a10a410f1d..6cd84d91b6 100755
--- a/build_image
+++ b/build_image
@@ -33,8 +33,8 @@ DEFINE_string base_pkg "coreos-base/coreos" \
   "The base portage package to base the build off of (only applies to prod images)"
 DEFINE_string base_dev_pkg "coreos-base/coreos-dev" \
   "The base portage package to base the build off of (only applies to dev containers)"
-DEFINE_string base_sysexts "app-containers/containerd,app-containers/docker" \
-  "Comma-separated list of packages to build into sysexts and include with OS image and update payload. Must be in order of dependencies, base sysexts come first."
+DEFINE_string base_sysexts "containerd-flatcar:app-containers/containerd,docker-flatcar:app-containers/docker" \
+  "Comma-separated list of name:package - build 'package' into sysext 'name', and include with OS image and update payload. Must be in order of dependencies, base sysexts come first."
 DEFINE_string output_root "${DEFAULT_BUILD_ROOT}/images" \
   "Directory in which to place image result directories (named by version)"
 DEFINE_string disk_layout "" \
diff --git a/build_library/prod_image_util.sh b/build_library/prod_image_util.sh
index 09fa70ac59..1f8029dc8c 100755
--- a/build_library/prod_image_util.sh
+++ b/build_library/prod_image_util.sh
@@ -179,30 +179,6 @@ EOF
       "${image_initrd_contents_wtd}" \
       "${image_disk_usage}"
 
-  # append sysext inventories to image contents files.
-  if [[ -n "${base_sysexts}" ]] ; then
-    local inventory_file="" image_basename="${image_name%.bin}"
-
-    for inventory_file in "${image_contents}" "${image_contents_wtd}" "${image_disk_usage}" "${image_packages}" ; do
-      local suffix="${inventory_file/${image_basename}/}" sysext=""
-
-      info "Processing '${inventory_file}'"
-
-      for sysext in ${base_sysexts//,/ }; do
-        local name="${sysext//\//_}"
-        local sysext_inventory="${root_fs_sysexts_output_dir}/${name}${suffix}"
-        if [[ ! -f "${sysext_inventory}" ]] ; then
-          die "Sysext inventory file '${sysext//\//_}${suffix}' for '${inventory_file}' not found in '${root_fs_sysexts_output_dir}'"
-        fi
-        info "Adding sysext inventory '${name}${suffix}' to '${inventory_file}'"
-        {
-          echo -e "\n\n### Sysext ${name}.raw\n"
-          cat "${sysext_inventory}"
-        } >> "${BUILD_DIR}/${inventory_file}"
-      done
-    done
-  fi
-
   # Upload
   local to_upload=(
     "${BUILD_DIR}/${image_contents}"
@@ -220,6 +196,24 @@ EOF
     "${BUILD_DIR}/${image_sysext_base}"
   )
 
+  # append sysext inventories to uploads
+  if [[ -n "${base_sysexts}" ]] ; then
+    local inventory_file="" image_basename="${image_name%.bin}"
+
+    for inventory_file in "${image_contents}" "${image_contents_wtd}" "${image_disk_usage}" "${image_packages}" ; do
+      local suffix="${inventory_file/${image_basename}/}" sysext=""
+
+      for sysext in ${base_sysexts//,/ }; do
+        local name="${sysext%:*}"
+        local sysext_inventory="${root_fs_sysexts_output_dir}/${name}${suffix}"
+        if [[ ! -f "${sysext_inventory}" ]] ; then
+          die "Sysext inventory file '${name}${suffix}' for '${inventory_file}' not found in '${root_fs_sysexts_output_dir}'"
+        fi
+        to_upload+=( "${sysext_inventory}" )
+      done
+    done
+  fi
+
   local files_to_evaluate=( "${BUILD_DIR}/${image_name}" )
   declare -a compressed_images
   declare -a extra_files
diff --git a/build_library/sysext_mangle_app-containers_containerd b/build_library/sysext_mangle_containerd-flatcar
similarity index 100%
rename from build_library/sysext_mangle_app-containers_containerd
rename to build_library/sysext_mangle_containerd-flatcar
diff --git a/build_library/sysext_mangle_app-containers_docker b/build_library/sysext_mangle_docker-flatcar
similarity index 100%
rename from build_library/sysext_mangle_app-containers_docker
rename to build_library/sysext_mangle_docker-flatcar
diff --git a/build_library/sysext_prod_builder b/build_library/sysext_prod_builder
index 4f9aacb3ad..a1db9acd7d 100755
--- a/build_library/sysext_prod_builder
+++ b/build_library/sysext_prod_builder
@@ -29,14 +29,14 @@ create_prod_sysext() {
   local workdir="$3"
   local base_sysext="$4"
   local install_root="$5"
-  local grp_pkg="$6"
-  local pkginfo="${7:-}"
+  local name="$6"
+  local grp_pkg="$7"
+  local pkginfo="${8:-}"
 
-  local name="${grp_pkg//\//_}" # some-group/some-package => some-group_some-package
   local pkginfo_opt=""
   local manglefs_opt=""
 
-  local msg="Creating sysext '${grp_pkg}' ==> ${name}.raw"
+  local msg="Installing ${grp_pkg}' in sysext ${name}.raw"
 
   # Include previous sysexts' pkginfo if supplied
   if [[ -n "${pkginfo}" ]] ; then
@@ -107,15 +107,18 @@ sudo mksquashfs "${root_fs_dir}" "${sysext_base}" -noappend
 # for combined overlay later.
 prev_pkginfo=""
 sysext_lowerdirs="${sysext_mountdir}/rootfs-lower"
-for grp_pkg in ${sysexts_list//,/ }; do
+for sysext in ${sysexts_list//,/ }; do
+  # format is "<name>:<group>/<package>"
+  name="${sysext%:*}"
+  grp_pkg="${sysext#*:}"
   create_prod_sysext "${BOARD}" \
                      "${sysext_output_dir}" \
                      "${sysext_workdir}" \
                      "${sysext_base}" \
                      "${root_fs_dir}"\
+                     "${name}" \
                      "${grp_pkg}" \
                      "${prev_pkginfo}"
-  name="${grp_pkg//\//_}"
 
   mkdir -p "${sysext_mountdir}/${name}" \
            "${sysext_mountdir}/${name}_pkginfo"