diff --git a/electrum/simple_config.py b/electrum/simple_config.py
index cd053b05b..5f9d462bd 100644
--- a/electrum/simple_config.py
+++ b/electrum/simple_config.py
@@ -925,9 +925,9 @@ class SimpleConfig(Logger):
     # config variables ----->
     NETWORK_AUTO_CONNECT = ConfigVar('auto_connect', default=True, type_=bool)
     NETWORK_ONESERVER = ConfigVar('oneserver', default=False, type_=bool)
-    NETWORK_PROXY = ConfigVar('proxy', default=None)
-    NETWORK_PROXY_USER = ConfigVar('proxy_user', default=None)
-    NETWORK_PROXY_PASSWORD = ConfigVar('proxy_password', default=None)
+    NETWORK_PROXY = ConfigVar('proxy', default=None, type_=str)
+    NETWORK_PROXY_USER = ConfigVar('proxy_user', default=None, type_=str)
+    NETWORK_PROXY_PASSWORD = ConfigVar('proxy_password', default=None, type_=str)
     NETWORK_SERVER = ConfigVar('server', default=None, type_=str)
     NETWORK_NOONION = ConfigVar('noonion', default=False, type_=bool)
     NETWORK_OFFLINE = ConfigVar('offline', default=False, type_=bool)