diff --git a/chroot_version_hooks.d/10_default_locales b/chroot_version_hooks.d/10_default_locales
new file mode 100644
index 0000000000..51d573ba07
--- /dev/null
+++ b/chroot_version_hooks.d/10_default_locales
@@ -0,0 +1,16 @@
+# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Make sure existing chroot's have default locales enabled
+# to match the new make_chroot behavior
+# http://crosbug.com/20378
+if ! grep -q -v -e '^#' -e '^$' /etc/locale.gen ; then
+  sudo_append /etc/locale.gen <<EOF
+en_US ISO-8859-1
+en_US.UTF-8 UTF-8
+EOF
+fi
+
+info "Chroot upgraded to version 10: Set default locale sets"
+exit 0
diff --git a/sdk_lib/enter_chroot.sh b/sdk_lib/enter_chroot.sh
index a9d12c3f71..67e9592ca4 100755
--- a/sdk_lib/enter_chroot.sh
+++ b/sdk_lib/enter_chroot.sh
@@ -336,13 +336,14 @@ function setup_env {
       esac
       gen_locales=("${gen_locales[@]}" "${l} ${enc}")
     done
-    # TODO(raymes): Something broke this with the new
-    # glibc. Need to uncomment this as soon as it's fixed.
-    # http://code.google.com/p/chromium-os/issues/detail?id=20378
-    #if [[ ${#gen_locales[@]} -gt 0 ]] ; then
-    #  sudo -- chroot "$FLAGS_chroot" locale-gen -q -u \
-    #    -G "$(printf '%s\n' "${gen_locales[@]}")"
-    #fi
+    if [[ ${#gen_locales[@]} -gt 0 ]] ; then
+      # Force LC_ALL=C to workaround slow string parsing in bash
+      # with long multibyte strings.  Newer setups have this fixed,
+      # but locale-gen doesn't need to be run in any locale in the
+      # first place, so just go with C to keep it fast.
+      sudo -- chroot "$FLAGS_chroot" env LC_ALL=C locale-gen -q -u \
+        -G "$(printf '%s\n' "${gen_locales[@]}")"
+    fi
 
     # Fix permissions on shared memory to allow non-root users access to POSIX
     # semaphores.