diff --git a/mindsdb_sql/render/sqlalchemy_render.py b/mindsdb_sql/render/sqlalchemy_render.py
index dc3f704..df08a26 100644
--- a/mindsdb_sql/render/sqlalchemy_render.py
+++ b/mindsdb_sql/render/sqlalchemy_render.py
@@ -538,7 +538,8 @@ def prepare_create_table(self, ast_query):
             if col.default is not None:
                 if isinstance(col.default, str):
                     default = sa.text(col.default)
-            if col.type.lower() == 'serial':
+
+            if isinstance(col.type, str) and col.type.lower() == 'serial':
                 col.is_primary_key = True
                 col.type = 'INT'