diff --git a/src/scripts/tutti/10_tasks.js b/src/scripts/tutti/10_tasks.js
index 6954fb0..289a920 100644
--- a/src/scripts/tutti/10_tasks.js
+++ b/src/scripts/tutti/10_tasks.js
@@ -121,6 +121,9 @@ function shot_create(project_url)
  */
 function task_add(shot_id, task_id, task_type)
 {
+    if (shot_id === undefined || task_id === undefined || task_type === undefined) {
+        throw new ReferenceError("task_add(" + shot_id + ", " + task_id + ", " + task_type + ") called.");
+    }
 
     var project_url = ProjectUtils.projectUrl();
     var url = '/attract/' + project_url + '/tasks/' + task_id;