diff --git a/endpoints/building.py b/endpoints/building.py
index bf2c2b161..b6d2f4904 100644
--- a/endpoints/building.py
+++ b/endpoints/building.py
@@ -8,6 +8,7 @@ from data import model
 from data.database import db
 from auth.auth_context import get_authenticated_user
 from endpoints.notificationhelper import spawn_notification
+from util.names import escape_tag
 
 
 logger = logging.getLogger(__name__)
@@ -160,7 +161,7 @@ class PreparedBuild(object):
     if self._tags:
       raise Exception('Property tags already set')
 
-    self._tags = list(value)
+    self._tags = [escape_tag(tag, default='latest') for tag in value]
 
   @property
   def build_name(self):
diff --git a/endpoints/v2/manifest.py b/endpoints/v2/manifest.py
index 3c87c199f..c30ae63f5 100644
--- a/endpoints/v2/manifest.py
+++ b/endpoints/v2/manifest.py
@@ -24,6 +24,7 @@ from endpoints.v2.errors import (BlobUnknown, ManifestInvalid, ManifestUnknown,
 from endpoints.trackhelper import track_and_log
 from endpoints.notificationhelper import spawn_notification
 from util.registry.replication import queue_storage_replication
+from util.names import VALID_TAG_PATTERN
 from digest import digest_tools
 from data import model
 from data.database import RepositoryTag
@@ -31,8 +32,6 @@ from data.database import RepositoryTag
 logger = logging.getLogger(__name__)
 
 
-VALID_TAG_PATTERN = r'[\w][\w.-]{0,127}'
-
 BASE_MANIFEST_ROUTE = '/<repopath:repository>/manifests/<regex("{0}"):manifest_ref>'
 MANIFEST_DIGEST_ROUTE = BASE_MANIFEST_ROUTE.format(digest_tools.DIGEST_PATTERN)
 MANIFEST_TAGNAME_ROUTE = BASE_MANIFEST_ROUTE.format(VALID_TAG_PATTERN)
diff --git a/test/test_digest_tools.py b/test/test_digest_tools.py
index 8fcb71237..fd873cefa 100644
--- a/test/test_digest_tools.py
+++ b/test/test_digest_tools.py
@@ -50,3 +50,8 @@ class TestDigestPath(unittest.TestCase):
 
     for digest, path in examples:
       self.assertEquals(content_path(digest), path)
+
+
+if __name__ == '__main__':
+  unittest.main()
+
diff --git a/test/test_names.py b/test/test_names.py
new file mode 100644
index 000000000..71de44046
--- /dev/null
+++ b/test/test_names.py
@@ -0,0 +1,20 @@
+import unittest
+
+from util.names import escape_tag
+
+class TestEscapeTag(unittest.TestCase):
+  def assertTag(self, input_tag, expected):
+    self.assertEquals(expected, escape_tag(input_tag))
+
+  def test_basic_tag(self):
+    self.assertTag('latest', 'latest')
+    self.assertTag('latest124', 'latest124')
+    self.assertTag('5de1e98d', '5de1e98d')
+
+  def test_invalid_tag(self):
+    self.assertTag('detailed_view#61', 'detailed_view_61')
+    self.assertTag('-detailed_view#61', '_detailed_view_61')
+
+if __name__ == '__main__':
+  unittest.main()
+
diff --git a/util/names.py b/util/names.py
index c943bfc52..e25eaa1c0 100644
--- a/util/names.py
+++ b/util/names.py
@@ -1,15 +1,26 @@
 import urllib
 import re
 
-from functools import wraps
 from uuid import uuid4
 
 REPOSITORY_NAME_REGEX = re.compile(r'^[\.a-zA-Z0-9_-]+$')
 
-TAG_REGEX = re.compile(r'^[\w][\w\.-]{0,127}$')
+VALID_TAG_PATTERN = r'[\w][\w.-]{0,127}'
+FULL_TAG_PATTERN = r'^[\w][\w.-]{0,127}$'
+
+TAG_REGEX = re.compile(FULL_TAG_PATTERN)
 TAG_ERROR = ('Invalid tag: must match [A-Za-z0-9_.-], NOT start with "." or "-", '
              'and can contain 1-128 characters')
 
+def escape_tag(tag, default='latest'):
+  """ Escapes a Docker tag, ensuring it matches the tag regular expression. """
+  if not tag:
+    return default
+
+  tag = re.sub(r'^[^\w]', '_', tag)
+  tag = re.sub(r'[^\w\.-]', '_', tag)
+  return tag[0:127]
+
 
 def parse_namespace_repository(repository, library_namespace, include_tag=False):
   parts = repository.rstrip('/').split('/', 1)