diff --git a/app/controllers/student_work_controller.rb b/app/controllers/student_work_controller.rb
index 9006c8a79..661770206 100644
--- a/app/controllers/student_work_controller.rb
+++ b/app/controllers/student_work_controller.rb
@@ -1096,7 +1096,7 @@ class StudentWorkController < ApplicationController
       all_student_ids = "(" + pro.members.map{|member| member.user_id}.join(",") + ")"
     end
     all_students = User.where("id in #{all_student_ids}")
-    student_work_id = @homework.student_work_projects.where("user_id=?",User.current.id).empty? ? -1 : @homework.student_work_projects.where("user_id=?",User.current.id).first.student_work_id
+    student_work_id = @homework.student_work_projects.where("user_id=? and student_work_id is not null",User.current.id).first.nil? ? -1 : @homework.student_work_projects.where("user_id=?",User.current.id).first.student_work_id
     @commit_student_ids = @homework.student_work_projects.where("student_work_id != #{student_work_id}").map{|student| student.user_id}
     @users = searchstudent_by_name all_students,name
     respond_to do |format|