diff --git a/sqlmodel/main.py b/sqlmodel/main.py
index b690915..46f3f0e 100644
--- a/sqlmodel/main.py
+++ b/sqlmodel/main.py
@@ -376,8 +376,9 @@ class SQLModelMetaclass(ModelMetaclass, DeclarativeMeta):
 
 
 def get_sqlalchemy_type(field: ModelField) -> Any:
-    if not issubclass(type(field.field_info.sa_type), type(Undefined)):
-        return field.field_info.sa_type
+    if hasattr(field.field_info, "sa_type"):
+        if not issubclass(type(field.field_info.sa_type), type(Undefined)):
+            return field.field_info.sa_type
     if issubclass(field.type_, str):
         if field.field_info.max_length:
             return AutoString(length=field.field_info.max_length)