diff --git a/tests/test_builder/test_koji.py b/tests/test_builder/test_koji.py
index 514c9eeb..e056bea0 100644
--- a/tests/test_builder/test_koji.py
+++ b/tests/test_builder/test_koji.py
@@ -66,7 +66,7 @@ class TestKojiBuilder(unittest.TestCase):
                                          module='nginx',
                                          config=conf,
                                          tag_name='module-nginx-1.2')
-        fake_kmb.module_target = {'build_tag': 'fake_tag'}
+        fake_kmb.module_target = {'build_tag': 'module-fake_tag'}
 
         with self.assertRaises(IOError):
             fake_kmb.buildroot_ready()
@@ -117,5 +117,6 @@ class FakeKojiSession(koji.ClientSession):
     def _setup_connection(self):
         pass
 
+    @module_build_service.utils.validate_koji_tag('tag')
     def getRepo(self, tag):
         return {'create_event': 'fake event'}
diff --git a/tests/test_utils/test_utils.py b/tests/test_utils/test_utils.py
index a9c0b298..2ee35213 100644
--- a/tests/test_utils/test_utils.py
+++ b/tests/test_utils/test_utils.py
@@ -26,6 +26,7 @@ from mock import patch
 import module_build_service.utils
 import module_build_service.scm
 from module_build_service import models
+from module_build_service.errors import ProgrammingError, ValidationError
 from tests import test_resuse_component_init_data, db
 
 BASE_DIR = path.abspath(path.dirname(__file__))
@@ -165,3 +166,50 @@ class TestUtils(unittest.TestCase):
         tangerine_rv = module_build_service.utils.get_reusable_component(
             db.session, second_module_build, 'tangerine')
         self.assertEqual(tangerine_rv, None)
+
+    def test_validate_koji_tag_wrong_tag_arg_during_programming(self):
+
+        @module_build_service.utils.validate_koji_tag('wrong_tag_arg')
+        def validate_koji_tag_programming_error(good_tag_arg, other_arg):
+            pass
+
+        with self.assertRaises(ProgrammingError):
+            validate_koji_tag_programming_error('dummy', 'other_val')
+
+    def test_validate_koji_tag_bad_tag_value(self):
+
+        @module_build_service.utils.validate_koji_tag('tag_arg')
+        def validate_koji_tag_bad_tag_value(tag_arg):
+            pass
+
+        with self.assertRaises(ValidationError):
+            validate_koji_tag_bad_tag_value('forbiddentagprefix-foo')
+
+    def test_validate_koji_tag_bad_tag_value_in_list(self):
+
+        @module_build_service.utils.validate_koji_tag('tag_arg')
+        def validate_koji_tag_bad_tag_value_in_list(tag_arg):
+            pass
+
+        with self.assertRaises(ValidationError):
+            validate_koji_tag_bad_tag_value_in_list([
+                'module-foo', 'forbiddentagprefix-bar'])
+
+    def test_validate_koji_tag_good_tag_value(self):
+
+        @module_build_service.utils.validate_koji_tag('tag_arg')
+        def validate_koji_tag_good_tag_value(tag_arg):
+            return True
+
+        self.assertEquals(
+            validate_koji_tag_good_tag_value('module-foo'), True)
+
+    def test_validate_koji_tag_good_tag_values_in_list(self):
+
+        @module_build_service.utils.validate_koji_tag('tag_arg')
+        def validate_koji_tag_good_tag_values_in_list(tag_arg):
+            return True
+
+        self.assertEquals(
+            validate_koji_tag_good_tag_values_in_list(['module-foo',
+                                                       'module-bar']), True)