diff --git a/models/issues/issue_search.go b/models/issues/issue_search.go
index e0b75d5adf..3a0815f7a5 100644
--- a/models/issues/issue_search.go
+++ b/models/issues/issue_search.go
@@ -183,14 +183,13 @@ func applyMilestoneCondition(sess *xorm.Session, opts *IssuesOptions) {
 }
 
 func applyProjectCondition(sess *xorm.Session, opts *IssuesOptions) {
-	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})))
-	} else if len(opts.ProjectIDs) > 0 { // specific project
-		sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
-			In("project_issue.project_id", opts.ProjectIDs)
+	if len(opts.ProjectIDs) > 0 { // specific project
+		if opts.ProjectIDs[0] == 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})))
+		} else {
+			sess.Join("INNER", "project_issue", "issue.id = project_issue.issue_id").
+				In("project_issue.project_id", opts.ProjectIDs)
+		}
 	}
 	// opts.ProjectID == 0 means all projects,
 	// do not need to apply any condition
diff --git a/modules/indexer/issues/dboptions.go b/modules/indexer/issues/dboptions.go
index c1f454eeee..c97ba545be 100644
--- a/modules/indexer/issues/dboptions.go
+++ b/modules/indexer/issues/dboptions.go
@@ -38,10 +38,10 @@ func ToSearchOptions(keyword string, opts *issues_model.IssuesOptions) *SearchOp
 		searchOpt.MilestoneIDs = opts.MilestoneIDs
 	}
 
-	if opts.ProjectID > 0 {
-		searchOpt.ProjectID = optional.Some(opts.ProjectID)
-	} else if opts.ProjectID == -1 { // FIXME: this is inconsistent from other places
-		searchOpt.ProjectID = optional.Some[int64](0) // Those issues with no project(projectid==0)
+	if len(opts.ProjectIDs) == 1 && opts.ProjectIDs[0] == db.NoConditionID {
+		searchOpt.ProjectIDs = []int64{0}
+	} else {
+		searchOpt.ProjectIDs = opts.ProjectIDs // Those issues with no project(projectid==0)
 	}
 
 	if opts.AssigneeID > 0 {