--- a/devtools/client/webconsole/new-console-output/test/fixtures/stub-generators/head.js
+++ b/devtools/client/webconsole/new-console-output/test/fixtures/stub-generators/head.js
@@ -76,17 +76,17 @@ function getCleanedPacket(key, packet) {
 
     if (res.message) {
       // Clean timeStamp on the message prop.
       res.message.timeStamp = existingPacket.message.timeStamp;
       if (res.message.timer) {
         // Clean timer properties on the message.
         // Those properties are found on console.time and console.timeEnd calls,
         // and those time can vary, which is why we need to clean them.
-        if (res.message.timer.duration) {
+        if ("duration" in res.message.timer) {
           res.message.timer.duration = existingPacket.message.timer.duration;
         }
       }
 
       if (Array.isArray(res.message.arguments)) {
         res.message.arguments = res.message.arguments.map((argument, i) => {
           if (!argument || typeof argument !== "object") {
             return argument;