diff --git a/lib/SerializerAppend2.js b/lib/SerializerAppend2.js
index 5dd42012..66111557 100644
--- a/lib/SerializerAppend2.js
+++ b/lib/SerializerAppend2.js
@@ -333,7 +333,9 @@ class Append2 {
       if (op.value !== null) {
         let content = op.value;
         if (typeof content !== 'string') {
-          content = JSON.stringify(content);
+          content = typeof content === 'bigint'
+            ? content.toString()
+            : JSON.stringify(content);
         }
         if (content.length < LARGE_CONTENT) {
           smallOutput.add(op.key, content);