diff --git a/keystonemiddleware/auth_token/__init__.py b/keystonemiddleware/auth_token/__init__.py
index f00ad9fc..79245c14 100644
--- a/keystonemiddleware/auth_token/__init__.py
+++ b/keystonemiddleware/auth_token/__init__.py
@@ -427,7 +427,10 @@ def _conf_values_type_convert(conf):
 
 
 def _get_project_version(project):
-    return pkg_resources.get_distribution(project).version
+    try:
+        return pkg_resources.get_distribution(project).version
+    except pkg_resources.DistributionNotFound:
+        return "unknown"
 
 
 def _uncompress_pkiz(token):
diff --git a/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py b/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py
index 628de092..2b49a309 100644
--- a/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py
+++ b/keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py
@@ -15,6 +15,7 @@
 import datetime
 import logging
 import os
+import pkg_resources
 import shutil
 import stat
 import tempfile
@@ -2474,6 +2475,19 @@ class TestAuthPluginUserAgentGeneration(BaseAuthTokenMiddlewareTest):
         project_with_version = '{0}/{1} '.format(project, project_version)
         self._assert_user_agent(app, project_with_version, project_version)
 
+    def test_project_not_installed_results_in_unknown_version(self):
+        project = uuid.uuid4().hex
+
+        conf = {'username': self.username,
+                'auth_url': self.auth_url,
+                'project': project}
+
+        v = pkg_resources.get_distribution('keystonemiddleware').version
+
+        app = self.create_simple_middleware(conf=conf, use_global_conf=True)
+        project_with_version = '{0}/{1} '.format(project, 'unknown')
+        self._assert_user_agent(app, project_with_version, v)
+
     def test_project_in_oslo_configuration(self):
         project = uuid.uuid4().hex
         project_version = uuid.uuid4().hex