diff --git a/lib/l10n_utils/dotlang.py b/lib/l10n_utils/dotlang.py
index e094d2f226..cb70416d53 100644
--- a/lib/l10n_utils/dotlang.py
+++ b/lib/l10n_utils/dotlang.py
@@ -25,7 +25,10 @@ from jinja2 import Markup
 from tower import tweak_message
 from product_details import product_details
 
+from lib.l10n_utils.utils import ContainsEverything
 
+
+ALL_THE_THINGS = ContainsEverything()
 FORMAT_IDENTIFIER_RE = re.compile(r"""(%
                                       (?:\((\w+)\))? # Mapping key
                                       s)""", re.VERBOSE)
@@ -230,6 +233,9 @@ def lang_file_tag_set(path, lang=None):
     :param lang: the language code or the lang of the request if omitted
     :return: set of strings
     """
+    if settings.DEV or lang == settings.LANGUAGE_CODE:
+        return ALL_THE_THINGS
+
     lang = lang or fix_case(translation.get_language())
     rel_path = os.path.join('locale', lang, '%s.lang' % path)
     cache_key = 'tag:%s' % rel_path
@@ -269,9 +275,6 @@ def lang_file_has_tag(path, lang=None, tag='active'):
        alphanumerics and "_".
     @return: bool
     """
-    if settings.DEV or lang == settings.LANGUAGE_CODE:
-        return True
-
     return tag in lang_file_tag_set(path, lang)
 
 
diff --git a/lib/l10n_utils/gettext.py b/lib/l10n_utils/gettext.py
index 0b8e675ed6..a81b3fe0a8 100644
--- a/lib/l10n_utils/gettext.py
+++ b/lib/l10n_utils/gettext.py
@@ -19,8 +19,10 @@ from jinja2 import Environment
 
 from dotlang import (parse as parse_lang, get_lang_path,
                      get_translations_for_langfile, lang_file_tag_set)
+from lib.l10n_utils.utils import ContainsEverything
 
 
+ALL_THE_THINGS = ContainsEverything()
 REGEX_URL = re.compile(r'.* (\S+/\S+\.[^:]+).*')
 cache = get_cache('l10n')
 
@@ -192,6 +194,9 @@ def template_tag_set(path, lang):
     :param lang: language code
     :return: set of strings
     """
+    if settings.DEV or lang == settings.LANGUAGE_CODE:
+        return ALL_THE_THINGS
+
     cache_key = 'template_tag_set:{path}:{lang}'.format(lang=lang, path=path)
     tag_set = cache.get(cache_key)
     if tag_set is None:
@@ -212,9 +217,6 @@ def template_has_tag(path, lang, tag):
     :param tag: the tag in question
     :return: boolean
     """
-    if settings.DEV:
-        return True
-
     return tag in template_tag_set(path, lang)
 
 
diff --git a/lib/l10n_utils/tests/test_gettext.py b/lib/l10n_utils/tests/test_gettext.py
index 18b6457d8e..a815c25ba7 100644
--- a/lib/l10n_utils/tests/test_gettext.py
+++ b/lib/l10n_utils/tests/test_gettext.py
@@ -15,7 +15,8 @@ from nose.tools import eq_, ok_
 
 from lib.l10n_utils.gettext import (_append_to_lang_file, langfiles_for_path,
                                     parse_python, parse_template,
-                                    po_msgs, pot_to_langfiles, template_is_active)
+                                    po_msgs, pot_to_langfiles, template_is_active,
+                                    _get_template_tag_set, template_has_tag)
 from lib.l10n_utils.tests import TempFileMixin
 from bedrock.mozorg.tests import TestCase
 
@@ -65,6 +66,16 @@ class TestTemplateTagFuncs(TestCase):
                                   get_lang_path):
         """Should return a unique set of tags from all lang files."""
         parse_template_mock.return_value = ['dude', 'walter']
+        lang_file_tag_set.side_effect = [set(['dude', 'donny']),
+                                         set(['dude', 'uli', 'bunny']),
+                                         set(['walter', 'brandt'])]
+        self.assertSetEqual(_get_template_tag_set('stuff', 'es'),
+                            set(['dude', 'walter', 'donny', 'uli', 'bunny', 'brandt']))
+
+    @override_settings(LANGUAGE_CODE='en-US')
+    def test_template_tag_set_default_locale(self):
+        """The default language should always have every tag."""
+        ok_(template_has_tag('the_dude', 'en-US', 'active'))
 
 
 class TestPOFiles(TestCase):
diff --git a/lib/l10n_utils/tests/test_utils.py b/lib/l10n_utils/tests/test_utils.py
new file mode 100644
index 0000000000..1a50fd46c6
--- /dev/null
+++ b/lib/l10n_utils/tests/test_utils.py
@@ -0,0 +1,16 @@
+# coding=utf-8
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from nose.tools import ok_
+
+from lib.l10n_utils.utils import ContainsEverything
+
+
+def test_contains_everything():
+    all_the_things = ContainsEverything()
+    ok_('dude' in all_the_things)
+    ok_(42 in all_the_things)
+    ok_(list in all_the_things)
diff --git a/lib/l10n_utils/utils.py b/lib/l10n_utils/utils.py
new file mode 100644
index 0000000000..47f3aef3ed
--- /dev/null
+++ b/lib/l10n_utils/utils.py
@@ -0,0 +1,11 @@
+# coding=utf-8
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+class ContainsEverything(object):
+    """An object whose instances will claim to contain anything."""
+    def __contains__(self, item):
+        return True