diff --git a/src/lib/types.ts b/src/lib/types.ts
index c22075b8..fba77ed9 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -436,7 +436,7 @@ export interface JSONEditorPropsOptional {
   askToFormat?: boolean
   escapeControlCharacters?: boolean
   escapeUnicodeCharacters?: boolean
-  flattenColumns?: true
+  flattenColumns?: boolean
   parser?: JSONParser
   validator?: Validator | null
   validationParser?: JSONParser