diff --git a/src/betterproto2_compiler/templates/template.py.j2 b/src/betterproto2_compiler/templates/template.py.j2
index ed2304a6..7ee3718b 100644
--- a/src/betterproto2_compiler/templates/template.py.j2
+++ b/src/betterproto2_compiler/templates/template.py.j2
@@ -235,7 +235,7 @@ class {{ service.py_name }}Base(ServiceBase):
 
     {% endfor %}
 
-    def __mapping__(self) -> "dict[str, grpclib.const.Handler":
+    def __mapping__(self) -> "dict[str, grpclib.const.Handler]":
         return {
         {% for method in service.methods %}
         "{{ method.route }}": grpclib.const.Handler(