diff --git a/models/issues/issue_search.go b/models/issues/issue_search.go
index 281339044b80..3640351a4d46 100644
--- a/models/issues/issue_search.go
+++ b/models/issues/issue_search.go
@@ -168,6 +168,18 @@ func applyMilestoneCondition(sess *xorm.Session, opts *IssuesOptions) *xorm.Sess
 	return sess
 }
 
+func applyProjectCondition(sess *xorm.Session, opts *IssuesOptions) *xorm.Session {
+	if opts.ProjectID > 0 { // specific project
+		sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
+			And("project_issue.project_id=?", opts.ProjectID)
+	} else if opts.ProjectID == db.NoConditionID { // show those that are in no project
+		sess.And(builder.NotIn("issue.id", builder.Select("issue_id").From("project_issue").And(builder.Neq{"project_id": 0})))
+	}
+	// opts.ProjectID == 0 means all projects,
+	// do not need to apply any condition
+	return sess
+}
+
 func applyRepoConditions(sess *xorm.Session, opts *IssuesOptions) *xorm.Session {
 	if len(opts.RepoIDs) == 1 {
 		opts.RepoCond = builder.Eq{"issue.repo_id": opts.RepoIDs[0]}
@@ -226,12 +238,7 @@ func applyConditions(sess *xorm.Session, opts *IssuesOptions) *xorm.Session {
 		sess.And(builder.Lte{"issue.updated_unix": opts.UpdatedBeforeUnix})
 	}
 
-	if opts.ProjectID > 0 {
-		sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
-			And("project_issue.project_id=?", opts.ProjectID)
-	} else if opts.ProjectID == db.NoConditionID { // show those that are in no project
-		sess.And(builder.NotIn("issue.id", builder.Select("issue_id").From("project_issue")))
-	}
+	applyProjectCondition(sess, opts)
 
 	if opts.ProjectBoardID != 0 {
 		if opts.ProjectBoardID > 0 {
diff --git a/models/issues/issue_stats.go b/models/issues/issue_stats.go
index d86123a824d6..6c249c224416 100644
--- a/models/issues/issue_stats.go
+++ b/models/issues/issue_stats.go
@@ -133,10 +133,7 @@ func getIssueStatsChunk(opts *IssuesOptions, issueIDs []int64) (*IssueStats, err
 
 		applyMilestoneCondition(sess, opts)
 
-		if opts.ProjectID > 0 {
-			sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
-				And("project_issue.project_id=?", opts.ProjectID)
-		}
+		applyProjectCondition(sess, opts)
 
 		if opts.AssigneeID > 0 {
 			applyAssigneeCondition(sess, opts.AssigneeID)
diff --git a/modules/indexer/issues/dboptions.go b/modules/indexer/issues/dboptions.go
index 6a41afadd707..d0ef1c96b448 100644
--- a/modules/indexer/issues/dboptions.go
+++ b/modules/indexer/issues/dboptions.go
@@ -17,6 +17,10 @@ func ToSearchOptions(keyword string, opts *issues_model.IssuesOptions) *SearchOp
 		IsClosed:  opts.IsClosed,
 	}
 
+	if opts.ProjectID != 0 {
+		searchOpt.ProjectID = &opts.ProjectID
+	}
+
 	if len(opts.LabelIDs) == 1 && opts.LabelIDs[0] == 0 {
 		searchOpt.NoLabelOnly = true
 	} else {