diff --git a/master/tasks.go b/master/tasks.go
index c3ea2d106..73347585c 100644
--- a/master/tasks.go
+++ b/master/tasks.go
@@ -305,6 +305,7 @@ func (t *FindItemNeighborsTask) run(j *task.JobsAllocator) error {
 		t.taskMonitor.Add(TaskFindItemNeighbors, len(dataset.ItemLabels))
 		// inverse document frequency of labels
 		for i := range labeledItems {
+			labeledItems[i] = lo.Uniq(labeledItems[i])
 			if dataset.ItemCount() == len(labeledItems[i]) {
 				labelIDF[i] = 1
 			} else {
@@ -646,6 +647,7 @@ func (t *FindUserNeighborsTask) run(j *task.JobsAllocator) error {
 		t.taskMonitor.Add(TaskFindUserNeighbors, len(dataset.UserLabels))
 		// inverse document frequency of labels
 		for i := range labeledUsers {
+			labeledUsers[i] = lo.Uniq(labeledUsers[i])
 			if dataset.UserCount() == len(labeledUsers[i]) {
 				labelIDF[i] = 1
 			} else {
diff --git a/master/tasks_test.go b/master/tasks_test.go
index 04e8aee88..03f8d2b49 100644
--- a/master/tasks_test.go
+++ b/master/tasks_test.go
@@ -256,8 +256,8 @@ func (s *MasterTestSuite) TestFindItemNeighborsIVF_ZeroIDF() {
 
 	// create dataset
 	err := s.DataClient.BatchInsertItems(ctx, []data.Item{
-		{"0", false, []string{"*"}, time.Now(), []string{"a"}, ""},
-		{"1", false, []string{"*"}, time.Now(), []string{"a"}, ""},
+		{"0", false, []string{"*"}, time.Now(), []string{"a", "a"}, ""},
+		{"1", false, []string{"*"}, time.Now(), []string{"a", "a"}, ""},
 	})
 	s.NoError(err)
 	err = s.DataClient.BatchInsertFeedback(ctx, []data.Feedback{
@@ -467,8 +467,8 @@ func (s *MasterTestSuite) TestFindUserNeighborsIVF_ZeroIDF() {
 
 	// create dataset
 	err := s.DataClient.BatchInsertUsers(ctx, []data.User{
-		{"0", []string{"a"}, nil, ""},
-		{"1", []string{"a"}, nil, ""},
+		{"0", []string{"a", "a"}, nil, ""},
+		{"1", []string{"a", "a"}, nil, ""},
 	})
 	s.NoError(err)
 	err = s.DataClient.BatchInsertFeedback(ctx, []data.Feedback{