diff --git a/arraycontext/container/dataclass.py b/arraycontext/container/dataclass.py
index bf433f283b991f6f9312bc86e88ff8ccd8173c7f..6549207684f32cceccf6b6f48ac9d2c8ed9288e6 100644
--- a/arraycontext/container/dataclass.py
+++ b/arraycontext/container/dataclass.py
@@ -46,10 +46,10 @@ def dataclass_array_container(cls: type) -> type:
     whether an attribute is an array container, the declared attribute type
     is checked by the criteria from :func:`is_array_container_type`.
     """
-    from dataclasses import is_dataclass
+    from dataclasses import is_dataclass, Field
     assert is_dataclass(cls)
 
-    def is_array_field(f):
+    def is_array_field(f: Field) -> bool:
         if __debug__:
             if not f.init:
                 raise ValueError(