diff --git a/src/updater/updateCoursesAndTeacherFeedbackTargets/updateCoursesAndTeacherFeedbackTargets.js b/src/updater/updateCoursesAndTeacherFeedbackTargets/updateCoursesAndTeacherFeedbackTargets.js
index fd5a4ef..debed5c 100644
--- a/src/updater/updateCoursesAndTeacherFeedbackTargets/updateCoursesAndTeacherFeedbackTargets.js
+++ b/src/updater/updateCoursesAndTeacherFeedbackTargets/updateCoursesAndTeacherFeedbackTargets.js
@@ -403,7 +403,10 @@ const getArchivedCoursesToDelete = async (courses) => {
 
 const coursesHandler = async (courses) => {
   // Filter out old AY courses. Already existing ones remain in db.
-  const courseUnits = [].concat(...courses.map((course) => course.courseUnits)).filter(({ code }) => code.startsWith('AY') && !code.match('^AY[0-9]+$'))
+  const courseUnits = courses
+    .flatMap((course) => course.courseUnits)
+    .filter(({ code }) => !(code.startsWith('AY') && !code.match('^AY[0-9]+$')))
+
   await createCourseUnits(courseUnits)
 
   const includeCurs = await getIncludeCurs()