diff --git a/src/core/buffer/BufferLine.ts b/src/core/buffer/BufferLine.ts
index ce3b54b7..91c3a8d1 100644
--- a/src/core/buffer/BufferLine.ts
+++ b/src/core/buffer/BufferLine.ts
@@ -217,7 +217,7 @@ export class AttributeData implements IAttributeData {
   }
 }
 
-export const DEFAULT_ATTR_DATA = new AttributeData();
+export const DEFAULT_ATTR_DATA = Object.freeze(new AttributeData());
 
 /**
  * CellData - represents a single Cell in the terminal buffer.