diff --git a/client/src/client/workers/test-evaluator.js b/client/src/client/workers/test-evaluator.js
index 30584bd40e..172b42e533 100644
--- a/client/src/client/workers/test-evaluator.js
+++ b/client/src/client/workers/test-evaluator.js
@@ -16,9 +16,16 @@ const __utils = (() => {
     }
   }
 
+  function replacer(key, value) {
+    if (Number.isNaN(value)) {
+      return 'NaN';
+    }
+    return value;
+  }
+
   const oldLog = self.console.log.bind(self.console);
   self.console.log = function proxyConsole(...args) {
-    logs.push(args.map(arg => '' + JSON.stringify(arg)).join(' '));
+    logs.push(args.map(arg => '' + JSON.stringify(arg, replacer)).join(' '));
     if (logs.join('\n').length > MAX_LOGS_SIZE) {
       flushLogs();
     }