diff --git a/frappyman.py b/frappyman.py
index d87f5f7..5a65fc6 100644
--- a/frappyman.py
+++ b/frappyman.py
@@ -83,21 +83,22 @@ class FrappyManager(ServiceManager):
 
     def prepare_start(self, ins, service, cfg=''):
         start_dir, env = super().prepare_start(ins, service)
+        env_update = {}
         for key, value in env.items():
              if '<SERV>' in value:
-                 env[key] = value.replace('<SERV>', service)
+                 env_update[key] = value.replace('<SERV>', service)
                  os.environ[key] = env[key]
         cfgpaths = self.config_dirs(ins, service)
         if cfgpaths:
-            env['FRAPPY_CONFDIR'] = os.pathsep.join(cfgpaths)
+            env_update['FRAPPY_CONFDIR'] = os.pathsep.join(cfgpaths)
         # merge PYTHONPATH from servicemanager.cfg with the one from environment
         pypathlist = []
         for pypath in env.get('PYTHONPATH'), os.environ.get('PYTHONPATH'):
             if pypath is not None:
                 pypathlist.extend(p for p in pypath.split(':') if p not in pypathlist)
         if pypathlist:
-            env['PYTHONPATH'] = os.environ['PYTHONPATH'] = ':'.join(pypathlist)
-        return start_dir, env
+            env_update['PYTHONPATH'] = os.environ['PYTHONPATH'] = ':'.join(pypathlist)
+        return start_dir, dict(env, **env_update)
 
     def do_start(self, ins, service=None, cfg='', restart=False, wait=False, logger=None):
         if self.wildcard(ins) is not None: