diff --git a/Makefile b/Makefile
index bc44adee9078be1df17d61424a4b96b1a7a28ca9..b7418f44708e509ebfb7300644a493b73ffb2b15 100644
--- a/Makefile
+++ b/Makefile
@@ -23,4 +23,4 @@ mypy:
 isort:
 	python3 -m isort $(MODULES)
 
-lint: black isort flake8
+lint: black isort flake8 mypy
diff --git a/ransack/transformer.py b/ransack/transformer.py
index dcb7de563278f09c872b7d7d4968bca894561bfa..35b7fc4a42b66107b876a1f5d29a6e6076adb3bc 100644
--- a/ransack/transformer.py
+++ b/ransack/transformer.py
@@ -695,7 +695,7 @@ class Filter(Interpreter):
 
         elif isinstance(data, MutableSequence):
             # Aggregate results from all list elements
-            aggregated = []
+            aggregated: Any = []
             for item in data:
                 if isinstance(item, (Mapping, MutableSequence)):
                     result, _ = self._get_data_value(path, item)