1 files changed, 2 insertions, 1 deletions
diff --git a/sqlglot/schema.py b/sqlglot/schema.py
index f6f3883..f5d9f2b 100644
--- a/sqlglot/schema.py
+++ b/sqlglot/schema.py
@@ -11,6 +11,7 @@ from sqlglot.trie import in_trie, new_trie
 
 if t.TYPE_CHECKING:
     from sqlglot.dataframe.sql.types import StructType
+    from sqlglot.dialects.dialect import DialectType
 
     ColumnMapping = t.Union[t.Dict, str, StructType, t.List]
 
@@ -153,7 +154,7 @@ class MappingSchema(AbstractMappingSchema[t.Dict[str, str]], Schema):
         self,
         schema: t.Optional[t.Dict] = None,
         visible: t.Optional[t.Dict] = None,
-        dialect: t.Optional[str] = None,
+        dialect: DialectType = None,
     ) -> None:
         self.dialect = dialect
         self.visible = visible or {}