diff --git a/app/models/group.rb b/app/models/group.rb
index 92a378e6e..1cfc6b56c 100644
--- a/app/models/group.rb
+++ b/app/models/group.rb
@@ -80,6 +80,8 @@ class Group < Principal
   def user_added(user)
     members.preload(:member_roles).each do |member|
       next if member.project_id.nil?
+      # skip if the group is a member without roles in the project
+      next if member.member_roles.empty?
 
       user_member =
         Member.find_or_initialize_by(:project_id => member.project_id, :user_id => user.id)
diff --git a/test/unit/group_test.rb b/test/unit/group_test.rb
index 92685e21c..9d7d037ab 100644
--- a/test/unit/group_test.rb
+++ b/test/unit/group_test.rb
@@ -177,4 +177,16 @@ class GroupTest < ActiveSupport::TestCase
 
     assert_equal %w(A B), Group.sorted.to_a.map(&:name)
   end
+
+  def test_user_added_should_not_fail_when_group_role_is_empty
+    group = Group.find(11)
+    project = Project.first
+    user = User.find(9)
+
+    m = Member.create!(:principal => group, :project => project, :role_ids => [1])
+    MemberRole.where(:member_id => m.id).delete_all
+
+    assert_nothing_raised {group.users << user}
+    assert group.users.include?(user)
+  end
 end