diff --git a/static/js/grab-canvas.js b/static/js/grab-canvas.js
index 002a8fb..3827ccf 100644
--- a/static/js/grab-canvas.js
+++ b/static/js/grab-canvas.js
@@ -3,6 +3,7 @@
 
     const currentScriptSrc = document.currentScript.src;
     const sourceElt = document.querySelector("canvas,video");
+    console.log("Grabbing", sourceElt)
 
     if(!sourceElt){
         console.error("No canvas found on this page")
@@ -41,6 +42,8 @@
     const canvasStreamTracks = canvasStream.getVideoTracks()
     if(canvasStreamTracks.length > 0){
         conn.addTrack(canvasStreamTracks[0], canvasStream)
+    } else {
+        throw new Error("Element don't habe video track")
     }
 
     const offer = await conn.createOffer();