diff --git a/app/models/course_member.rb b/app/models/course_member.rb
index 52c13dbbf..65849e5de 100644
--- a/app/models/course_member.rb
+++ b/app/models/course_member.rb
@@ -148,7 +148,7 @@ class CourseMember < ApplicationRecord
     if teacher_groups.count > 0
       member_ids = teacher_groups.where(course_group_id: self.try(:course_group_id)).pluck(:course_member_id).compact
 
-      none_group_teachers = teacher_groups.pluck(:course_member_id).size > 0 ? teacher_groups.pluck(:course_member_id).compact.join(',') : -1
+      none_group_teachers = teacher_groups.pluck(:course_member_id).compact.size > 0 ? teacher_groups.pluck(:course_member_id).compact.join(',') : -1
       teachers = course.teachers.where("course_members.id not in (#{none_group_teachers}) or
                                             course_members.id in (#{member_ids.size > 0 ? member_ids.join(',') : -1})")
     else