diff --git a/seatable_api/constants.py b/seatable_api/constants.py
index 78617ce..eff3729 100644
--- a/seatable_api/constants.py
+++ b/seatable_api/constants.py
@@ -18,7 +18,7 @@
 
 ##### column types #####
 @unique
-class ColumnTypes(Enum):
+class ColumnTypes(str, Enum):
     DEFAULT = 'default'
     NUMBER = 'number'
     TEXT = 'text'