diff --git a/shell/watcher.js b/shell/watcher.js
index 19425c6..514b16b 100644
--- a/shell/watcher.js
+++ b/shell/watcher.js
@@ -47,7 +47,7 @@ function processMessage(message) {
   console.log(message);
   try {
     const { variable, value } = JSON.parse(message);
-    const diff = calculateDiff(progvars[variable], value);
+    const diff = JSON.stringify(calculateDiff(progvars[variable], value));
     send_ws_message(diff);
     progvars[variable] = value;