diff --git a/src/opengnsys/workers/server_worker.py b/src/opengnsys/workers/server_worker.py
index 959dcc9..57c913f 100644
--- a/src/opengnsys/workers/server_worker.py
+++ b/src/opengnsys/workers/server_worker.py
@@ -97,7 +97,7 @@ class ServerWorker(object):
         try:
             operation = getattr(self, 'process_' + path[0])
         except:
-            raise Exception ({ '_httpcode': 404, '_msg': '{path[0]}: method not found' })
+            raise Exception ({ '_httpcode': 404, '_msg': f'{path[0]}: method not found' })
         
         return operation(path[1:], getParams, postParams, server)