diff --git a/pandas/core/arrays/_mixins.py b/pandas/core/arrays/_mixins.py
index cb018103d07b4..3fe2d56a2ccb2 100644
--- a/pandas/core/arrays/_mixins.py
+++ b/pandas/core/arrays/_mixins.py
@@ -182,6 +182,7 @@ def equals(self, other) -> bool:
             return False
         return bool(array_equivalent(self._ndarray, other._ndarray))
 
+    @classmethod
     def _from_factorized(cls, values, original):
         assert values.dtype == original._ndarray.dtype
         return original._from_backing_data(values)
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 971ee38005673..d717e5cfb1083 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -3932,10 +3932,7 @@ def _get_indexer(
             else:
                 tgt_values = target._get_engine_target()
 
-            # error: Argument 1 to "get_indexer" of "IndexEngine" has incompatible
-            # type "Union[ExtensionArray, ndarray[Any, Any]]"; expected
-            # "ndarray[Any, Any]"
-            indexer = self._engine.get_indexer(tgt_values)  # type: ignore[arg-type]
+            indexer = self._engine.get_indexer(tgt_values)
 
         return ensure_platform_int(indexer)