--- a/devtools/server/tests/mochitest/test_memory_gc_01.html
+++ b/devtools/server/tests/mochitest/test_memory_gc_01.html
@@ -27,21 +27,21 @@ window.onload = function () {
       let objects = [];
       for (let i = 0; i < 1000; i++) {
         let o = {};
         o[Math.random()] = 1;
         objects.push(o);
       }
       objects = null;
 
-      await { total: beforeGC } = memory.measure();
+      beforeGC = (await memory.measure()).total;
 
       await memory.forceGarbageCollection();
 
-      await { total: afterGC } = memory.measure();
+      afterGC = (await memory.measure()).total;
     } while (beforeGC < afterGC);
 
     ok(true, "The amount of memory after GC should eventually decrease");
 
     destroyServerAndFinish(client);
   })();
 };
 </script>