diff --git a/src/flask/app.py b/src/flask/app.py
index 7622b5e8..5c424b13 100644
--- a/src/flask/app.py
+++ b/src/flask/app.py
@@ -1226,7 +1226,7 @@ class Flask(App):
 
         # extend existing headers with provided headers
         if headers:
-            rv.headers.update(headers)  # type: ignore[arg-type]
+            rv.headers.update(headers)
 
         return rv