diff --git a/mistral/cmd/launch.py b/mistral/cmd/launch.py
index b6b159722..ec79816ae 100644
--- a/mistral/cmd/launch.py
+++ b/mistral/cmd/launch.py
@@ -143,7 +143,7 @@ MISTRAL_TITLE = """
 ||      || || __//   ||_// ||      \\\__// \\\_ ||
 
 Mistral Workflow Service, version %s
-""" % version.version_string()
+""" % version.version_string
 
 
 def print_server_info():
diff --git a/mistral/tests/unit/test_version.py b/mistral/tests/unit/test_version.py
new file mode 100644
index 000000000..676fa8d67
--- /dev/null
+++ b/mistral/tests/unit/test_version.py
@@ -0,0 +1,19 @@
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+
+from mistral.tests.unit import base
+from mistral.version import version_string
+
+
+class VersionStringTest(base.BaseTest):
+    def test_version(self):
+        self.assertIsInstance(version_string, str)
diff --git a/mistral/version.py b/mistral/version.py
index 892b7b9ee..40ba471c7 100644
--- a/mistral/version.py
+++ b/mistral/version.py
@@ -15,4 +15,4 @@
 from pbr import version
 
 version_info = version.VersionInfo('mistral')
-version_string = version_info.version_string
+version_string = version_info.version_string()