diff --git a/api-ref/source/os-server-tags.inc b/api-ref/source/os-server-tags.inc
index 69afbed4eb5f..c672ccedc875 100644
--- a/api-ref/source/os-server-tags.inc
+++ b/api-ref/source/os-server-tags.inc
@@ -13,6 +13,8 @@ Tags have the following restrictions:
 
 -  Tag is a Unicode bytestring no longer than 60 characters.
 
+-  Tag is a non-empty string.
+
 -  Tags are case sensitive.
 
 -  '/' is not allowed to be in a tag name
diff --git a/nova/api/openstack/compute/server_tags.py b/nova/api/openstack/compute/server_tags.py
index d21061d3c976..521c2affa83d 100644
--- a/nova/api/openstack/compute/server_tags.py
+++ b/nova/api/openstack/compute/server_tags.py
@@ -94,9 +94,9 @@ class ServerTagsController(wsgi.Controller):
         try:
             jsonschema.validate(id, parameter_types.tag)
         except jsonschema.ValidationError as e:
-            msg = (_("Tag '%(tag)s' is invalid. It must be a string without "
-                     "characters '/' and ','. Validation error message: "
-                     "%(err)s") % {'tag': id, 'err': e.message})
+            msg = (_("Tag '%(tag)s' is invalid. It must be a non empty string "
+                     "without characters '/' and ','. Validation error "
+                     "message: %(err)s") % {'tag': id, 'err': e.message})
             raise webob.exc.HTTPBadRequest(explanation=msg)
 
         try:
diff --git a/nova/api/validation/parameter_types.py b/nova/api/validation/parameter_types.py
index 7340139cfef8..f417965c217a 100644
--- a/nova/api/validation/parameter_types.py
+++ b/nova/api/validation/parameter_types.py
@@ -399,6 +399,6 @@ personality = {
 
 tag = {
     "type": "string",
-    "maxLength": tag.MAX_TAG_LENGTH,
+    "minLength": 1, "maxLength": tag.MAX_TAG_LENGTH,
     "pattern": "^[^,/]*$"
 }
diff --git a/nova/tests/unit/api/openstack/compute/test_server_tags.py b/nova/tests/unit/api/openstack/compute/test_server_tags.py
index 06e325c1ef68..28d3fab54cf3 100644
--- a/nova/tests/unit/api/openstack/compute/test_server_tags.py
+++ b/nova/tests/unit/api/openstack/compute/test_server_tags.py
@@ -121,6 +121,12 @@ class ServerTagsTest(test.TestCase):
                           self.controller.update_all,
                           req, UUID, body={'tags': [1]})
 
+    def test_update_all_tags_with_one_tag_empty_string(self):
+        req = self._get_request('/v2/fake/servers/%s/tags' % UUID, 'PUT')
+        self.assertRaises(exception.ValidationError,
+                          self.controller.update_all,
+                          req, UUID, body={'tags': ['tag1', '']})
+
     def test_update_all_too_long_tag(self):
         self.stub_out('nova.api.openstack.common.get_instance', return_server)
         req = self._get_request('/v2/fake/servers/%s/tags' % UUID, 'PUT')