diff --git a/src/renderer/sigFrameScript.js b/src/renderer/sigFrameScript.js
index 512c1b73f..b37f26fec 100644
--- a/src/renderer/sigFrameScript.js
+++ b/src/renderer/sigFrameScript.js
@@ -12,7 +12,7 @@ window.addEventListener('message', (event) => {
   } catch (error) {
     window.parent.postMessage(JSON.stringify({
       id: data.id,
-      error
+      error: error.toString()
     }), '*')
   }
 })