diff --git a/src/keycloak/keycloak_admin.py b/src/keycloak/keycloak_admin.py
index 56b415e..1334df2 100644
--- a/src/keycloak/keycloak_admin.py
+++ b/src/keycloak/keycloak_admin.py
@@ -84,7 +84,7 @@ class KeycloakAdmin:
     PAGE_SIZE = 100
 
     _auto_refresh_token = None
-    _connection = None
+    _connection: Optional[KeycloakOpenIDConnection] = None
 
     def __init__(
         self,