diff --git a/pillar/application/utils/__init__.py b/pillar/application/utils/__init__.py
index 42ef8423..4a444375 100644
--- a/pillar/application/utils/__init__.py
+++ b/pillar/application/utils/__init__.py
@@ -4,9 +4,11 @@ import datetime
 import functools
 import logging
 
-import bson
+import bson.objectid
 from eve import RFC1123_DATE_FORMAT
 from flask import current_app
+from werkzeug import exceptions as wz_exceptions
+
 
 __all__ = ('remove_private_keys', 'PillarJSONEncoder')
 log = logging.getLogger(__name__)
@@ -80,3 +82,20 @@ def project_get_node_type(project_document, node_type_node_name):
 
     return next((node_type for node_type in project_document['node_types']
                  if node_type['name'] == node_type_node_name), None)
+
+
+def str2id(document_id):
+    """Returns the document ID as ObjectID, or raises a BadRequest exception.
+
+    :type document_id: str
+    :rtype: bson.ObjectId
+    :raises: wz_exceptions.BadRequest
+    """
+
+    if not document_id:
+        raise wz_exceptions.BadRequest('Invalid object ID %r', document_id)
+
+    try:
+        return bson.ObjectId(document_id)
+    except bson.objectid.InvalidId:
+        raise wz_exceptions.BadRequest('Invalid object ID %r', document_id)
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 00000000..e616e148
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,31 @@
+# -*- encoding: utf-8 -*-
+
+from bson import ObjectId
+from werkzeug.exceptions import BadRequest
+
+from common_test_class import AbstractPillarTest
+
+
+class Str2idTest(AbstractPillarTest):
+    def test_happy(self):
+        from application.utils import str2id
+
+        def happy(str_id):
+            self.assertEqual(ObjectId(str_id), str2id(str_id))
+
+        happy(24 * 'a')
+        happy(12 * 'a')
+        happy(u'577e23ad98377323f74c368c')
+
+    def test_unhappy(self):
+        from application.utils import str2id
+
+        def unhappy(str_id):
+            self.assertRaises(BadRequest, str2id, str_id)
+
+        unhappy(13 * 'a')
+        unhappy(u'577e23ad 8377323f74c368c')
+        unhappy(u'김치')  # Kimchi
+        unhappy('')
+        unhappy(u'')
+        unhappy(None)