diff --git a/lib/script/witness.js b/lib/script/witness.js
index 632377327..c4ed87a3b 100644
--- a/lib/script/witness.js
+++ b/lib/script/witness.js
@@ -433,7 +433,7 @@ class Witness extends Stack {
   toJSON() {
     let result = this.toRaw().toString('hex');
     if (result === '00') {
-      result = null;
+      result = '';
     }
     return result;
   }