diff --git a/openhtf/output/servers/station_server.py b/openhtf/output/servers/station_server.py
index 690edd523..66b8324c0 100644
--- a/openhtf/output/servers/station_server.py
+++ b/openhtf/output/servers/station_server.py
@@ -456,7 +456,8 @@ def get(self):
     for file_name in os.listdir(self.history_path):
       if not file_name.endswith('.pb'):
         continue
-
+      if self.history_path is None:
+        raise ValueError('history_path is None, try calling initialize() first')
       if not os.path.isfile(os.path.join(self.history_path, file_name)):
         continue