diff --git a/dlt/extract/incremental/__init__.py b/dlt/extract/incremental/__init__.py
index f0c6803b51..5e7bae49c6 100644
--- a/dlt/extract/incremental/__init__.py
+++ b/dlt/extract/incremental/__init__.py
@@ -517,7 +517,7 @@ def __str__(self) -> str:
             f" {self.last_value_func}"
         )
 
-    def _make_transformer(self, cls: Type[IncrementalTransform]) -> IncrementalTransform:
+    def _make_or_get_transformer(self, cls: Type[IncrementalTransform]) -> IncrementalTransform:
         if transformer := self._transformers.get(cls):
             return transformer
         transformer = self._transformers[cls] = cls(
@@ -540,11 +540,11 @@ def _get_transformer(self, items: TDataItems) -> IncrementalTransform:
         # Assume list is all of the same type
         for item in items if isinstance(items, list) else [items]:
             if is_arrow_item(item):
-                return self._make_transformer(ArrowIncremental)
+                return self._make_or_get_transformer(ArrowIncremental)
             elif pandas is not None and isinstance(item, pandas.DataFrame):
-                return self._make_transformer(ArrowIncremental)
-            return self._make_transformer(JsonIncremental)
-        return self._make_transformer(JsonIncremental)
+                return self._make_or_get_transformer(ArrowIncremental)
+            return self._make_or_get_transformer(JsonIncremental)
+        return self._make_or_get_transformer(JsonIncremental)
 
     def __call__(self, rows: TDataItems, meta: Any = None) -> Optional[TDataItems]:
         if rows is None:
diff --git a/tests/extract/test_incremental.py b/tests/extract/test_incremental.py
index 5c96098343..3ebc9d1201 100644
--- a/tests/extract/test_incremental.py
+++ b/tests/extract/test_incremental.py
@@ -3864,7 +3864,7 @@ def test_start_range_open(item_type: TestDataItemFormat, last_value_func: Any) -
         expected_items = list(range(6, 12))
         order_dir = "ASC"
     elif last_value_func == min:
-        data_range = reversed(data_range)
+        data_range = reversed(data_range)  # type: ignore[call-overload]
         initial_value = 5
         # Only items lower than inital extracted
         expected_items = list(reversed(range(1, 5)))
diff --git a/tests/load/sources/sql_database/test_sql_database_source.py b/tests/load/sources/sql_database/test_sql_database_source.py
index 9079638586..b5d4e000ae 100644
--- a/tests/load/sources/sql_database/test_sql_database_source.py
+++ b/tests/load/sources/sql_database/test_sql_database_source.py
@@ -13,6 +13,7 @@
 from dlt.common.utils import uniq_id
 
 from dlt.extract.exceptions import ResourceExtractionError
+from dlt.extract.incremental.transform import JsonIncremental, ArrowIncremental
 from dlt.sources import DltResource
 
 from tests.pipeline.utils import (
@@ -831,8 +832,8 @@ def _assert_incremental(item):
         else:
             assert _r.incremental.primary_key == ["id"]
         assert _r.incremental._incremental.primary_key == ["id"]
-        assert _r.incremental._incremental._transformers["json"].primary_key == ["id"]
-        assert _r.incremental._incremental._transformers["arrow"].primary_key == ["id"]
+        assert _r.incremental._incremental._make_or_get_transformer(JsonIncremental).primary_key == ["id"]
+        assert _r.incremental._incremental._make_or_get_transformer(ArrowIncremental).primary_key == ["id"]
         return item
 
     pipeline = make_pipeline("duckdb")
@@ -841,8 +842,8 @@ def _assert_incremental(item):
 
     assert resource.incremental.primary_key == ["id"]
     assert resource.incremental._incremental.primary_key == ["id"]
-    assert resource.incremental._incremental._transformers["json"].primary_key == ["id"]
-    assert resource.incremental._incremental._transformers["arrow"].primary_key == ["id"]
+    assert resource.incremental._incremental._make_or_get_transformer(JsonIncremental).primary_key == ["id"]
+    assert resource.incremental._incremental._make_or_get_transformer(ArrowIncremental).primary_key == ["id"]
 
 
 @pytest.mark.parametrize("backend", ["sqlalchemy", "pyarrow", "pandas", "connectorx"])