diff --git a/models/issue_reaction.go b/models/issue_reaction.go
index 50b9d6848..104afce5c 100644
--- a/models/issue_reaction.go
+++ b/models/issue_reaction.go
@@ -17,13 +17,13 @@ import (
 
 // Reaction represents a reactions on issues and comments.
 type Reaction struct {
-	ID               int64  `xorm:"pk autoincr"`
-	Type             string `xorm:"INDEX UNIQUE(s) NOT NULL"`
-	IssueID          int64  `xorm:"INDEX UNIQUE(s) NOT NULL"`
-	CommentID        int64  `xorm:"INDEX UNIQUE(s)"`
-	UserID           int64  `xorm:"INDEX UNIQUE(s) NOT NULL"`
-	OriginalAuthorID int64  `xorm:"INDEX UNIQUE(s) NOT NULL DEFAULT(0)"`
-	OriginalAuthor   string
+	ID               int64              `xorm:"pk autoincr"`
+	Type             string             `xorm:"INDEX UNIQUE(s) NOT NULL"`
+	IssueID          int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
+	CommentID        int64              `xorm:"INDEX UNIQUE(s)"`
+	UserID           int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
+	OriginalAuthorID int64              `xorm:"INDEX UNIQUE(s) NOT NULL DEFAULT(0)"`
+	OriginalAuthor   string             `xorm:"INDEX UNIQUE(s)"`
 	User             *User              `xorm:"-"`
 	CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
 }
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index 4715f192c..5a2646474 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -252,6 +252,8 @@ var migrations = []Migration{
 	NewMigration("ensure repo topics are up-to-date", fixRepoTopics),
 	// v158 -> v159
 	NewMigration("code comment replies should have the commitID of the review they are replying to", updateCodeCommentReplies),
+	// v159 -> v160
+	NewMigration("update reactions constraint", updateReactionConstraint),
 }
 
 // GetCurrentDBVersion returns the current db version
diff --git a/models/migrations/v159.go b/models/migrations/v159.go
new file mode 100644
index 000000000..68043b941
--- /dev/null
+++ b/models/migrations/v159.go
@@ -0,0 +1,38 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func updateReactionConstraint(x *xorm.Engine) error {
+	// Reaction represents a reactions on issues and comments.
+	type Reaction struct {
+		ID               int64              `xorm:"pk autoincr"`
+		Type             string             `xorm:"INDEX UNIQUE(s) NOT NULL"`
+		IssueID          int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
+		CommentID        int64              `xorm:"INDEX UNIQUE(s)"`
+		UserID           int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
+		OriginalAuthorID int64              `xorm:"INDEX UNIQUE(s) NOT NULL DEFAULT(0)"`
+		OriginalAuthor   string             `xorm:"INDEX UNIQUE(s)"`
+		CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := recreateTable(sess, &Reaction{}); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}