diff --git a/plugins/jspsych-html.js b/plugins/jspsych-html.js
index ff4f5ab9..b373c28f 100644
--- a/plugins/jspsych-html.js
+++ b/plugins/jspsych-html.js
@@ -56,7 +56,7 @@ Example Usage:
             // if any trial variables are functions
             // this evaluates the function and replaces
             // it with the output of the function
-            // trial = jsPsych.normalizeTrialVariables(trial);
+            trial = jsPsych.normalizeTrialVariables(trial, ["check_fn"]);
 
             var url = trial.url;
             if (trial.force_refresh) {