diff --git a/src/werkzeug/datastructures.py b/src/werkzeug/datastructures.py
index 43ee8c754..a293dfddb 100644
--- a/src/werkzeug/datastructures.py
+++ b/src/werkzeug/datastructures.py
@@ -1226,7 +1226,7 @@ def __setitem__(self, key, value):
                 (_unicodify_header_value(k), _unicodify_header_value(v))
                 for (k, v) in value
             ]
-            for (_, v) in value:
+            for _, v in value:
                 self._validate_value(v)
             if isinstance(key, int):
                 self._list[key] = value[0]