diff --git a/yarn-project/foundation/src/json-rpc/convert.ts b/yarn-project/foundation/src/json-rpc/convert.ts
index bcd5b15d3c7..53a3fe0d3b3 100644
--- a/yarn-project/foundation/src/json-rpc/convert.ts
+++ b/yarn-project/foundation/src/json-rpc/convert.ts
@@ -117,6 +117,14 @@ export function convertFromJsonObj(cc: ClassConverter, obj: any): any {
  * @returns The encoded object.
  */
 export function convertToJsonObj(cc: ClassConverter, obj: any): any {
+  // Bigint is a primitive type that needs special handling since it's not serialisable
+  if (typeof obj === 'bigint') {
+    return {
+      type: 'bigint',
+      data: obj.toString(),
+    };
+  }
+
   if (!obj) {
     return obj; // Primitive type
   }
@@ -126,13 +134,6 @@ export function convertToJsonObj(cc: ClassConverter, obj: any): any {
     return { type: 'Buffer', data: obj.toString('base64') };
   }
 
-  if (typeof obj === 'bigint') {
-    return {
-      type: 'bigint',
-      data: obj.toString(),
-    };
-  }
-
   // Is this a convertible type?
   if (cc.isRegisteredClass(obj.constructor)) {
     return cc.toJsonObj(obj);