diff --git a/models/error.go b/models/error.go
index 995617e83b8..be23b47b877 100644
--- a/models/error.go
+++ b/models/error.go
@@ -1104,6 +1104,21 @@ func (err ErrNewIssueInsert) Error() string {
 	return err.OriginalError.Error()
 }
 
+// ErrReactionAlreadyExist is used when a existing reaction was try to created
+type ErrReactionAlreadyExist struct {
+	Reaction string
+}
+
+// IsErrReactionAlreadyExist checks if an error is a ErrReactionAlreadyExist.
+func IsErrReactionAlreadyExist(err error) bool {
+	_, ok := err.(ErrReactionAlreadyExist)
+	return ok
+}
+
+func (err ErrReactionAlreadyExist) Error() string {
+	return fmt.Sprintf("reaction '%s' already exists", err.Reaction)
+}
+
 // __________      .__  .__ __________                                     __
 // \______   \__ __|  | |  |\______   \ ____  ________ __   ____   _______/  |_
 //  |     ___/  |  \  | |  | |       _// __ \/ ____/  |  \_/ __ \ /  ___/\   __\
diff --git a/models/issue_reaction.go b/models/issue_reaction.go
index ab644b4b3ea..a0dc7285109 100644
--- a/models/issue_reaction.go
+++ b/models/issue_reaction.go
@@ -30,6 +30,8 @@ type Reaction struct {
 type FindReactionsOptions struct {
 	IssueID   int64
 	CommentID int64
+	UserID    int64
+	Reaction  string
 }
 
 func (opts *FindReactionsOptions) toConds() builder.Cond {
@@ -40,6 +42,13 @@ func (opts *FindReactionsOptions) toConds() builder.Cond {
 	if opts.CommentID > 0 {
 		cond = cond.And(builder.Eq{"reaction.comment_id": opts.CommentID})
 	}
+	if opts.UserID > 0 {
+		cond = cond.And(builder.Eq{"reaction.user_id": opts.UserID})
+	}
+	if opts.Reaction != "" {
+		cond = cond.And(builder.Eq{"reaction.type": opts.Reaction})
+	}
+
 	return cond
 }
 
@@ -57,9 +66,25 @@ func createReaction(e *xorm.Session, opts *ReactionOptions) (*Reaction, error) {
 		UserID:  opts.Doer.ID,
 		IssueID: opts.Issue.ID,
 	}
+	findOpts := FindReactionsOptions{
+		IssueID:   opts.Issue.ID,
+		CommentID: -1, // reaction to issue only
+		Reaction:  opts.Type,
+		UserID:    opts.Doer.ID,
+	}
 	if opts.Comment != nil {
 		reaction.CommentID = opts.Comment.ID
+		findOpts.CommentID = opts.Comment.ID
 	}
+
+	existingR, err := findReactions(e, findOpts)
+	if err != nil {
+		return nil, err
+	}
+	if len(existingR) > 0 {
+		return existingR[0], ErrReactionAlreadyExist{Reaction: opts.Type}
+	}
+
 	if _, err := e.Insert(reaction); err != nil {
 		return nil, err
 	}
@@ -76,19 +101,19 @@ type ReactionOptions struct {
 }
 
 // CreateReaction creates reaction for issue or comment.
-func CreateReaction(opts *ReactionOptions) (reaction *Reaction, err error) {
+func CreateReaction(opts *ReactionOptions) (*Reaction, error) {
 	sess := x.NewSession()
 	defer sess.Close()
-	if err = sess.Begin(); err != nil {
+	if err := sess.Begin(); err != nil {
 		return nil, err
 	}
 
-	reaction, err = createReaction(sess, opts)
+	reaction, err := createReaction(sess, opts)
 	if err != nil {
-		return nil, err
+		return reaction, err
 	}
 
-	if err = sess.Commit(); err != nil {
+	if err := sess.Commit(); err != nil {
 		return nil, err
 	}
 	return reaction, nil
diff --git a/models/issue_reaction_test.go b/models/issue_reaction_test.go
index bbd8cf29fec..a2f1c025f2f 100644
--- a/models/issue_reaction_test.go
+++ b/models/issue_reaction_test.go
@@ -50,9 +50,10 @@ func TestIssueAddDuplicateReaction(t *testing.T) {
 		Type:  "heart",
 	})
 	assert.Error(t, err)
-	assert.Nil(t, reaction)
+	assert.Equal(t, ErrReactionAlreadyExist{Reaction: "heart"}, err)
 
-	AssertExistsAndLoadBean(t, &Reaction{Type: "heart", UserID: user1.ID, IssueID: issue1.ID})
+	existingR := AssertExistsAndLoadBean(t, &Reaction{Type: "heart", UserID: user1.ID, IssueID: issue1.ID}).(*Reaction)
+	assert.Equal(t, existingR.ID, reaction.ID)
 }
 
 func TestIssueDeleteReaction(t *testing.T) {
@@ -129,7 +130,6 @@ func TestIssueCommentDeleteReaction(t *testing.T) {
 	user2 := AssertExistsAndLoadBean(t, &User{ID: 2}).(*User)
 	user3 := AssertExistsAndLoadBean(t, &User{ID: 3}).(*User)
 	user4 := AssertExistsAndLoadBean(t, &User{ID: 4}).(*User)
-	ghost := NewGhostUser()
 
 	issue1 := AssertExistsAndLoadBean(t, &Issue{ID: 1}).(*Issue)
 
@@ -139,14 +139,13 @@ func TestIssueCommentDeleteReaction(t *testing.T) {
 	addReaction(t, user2, issue1, comment1, "heart")
 	addReaction(t, user3, issue1, comment1, "heart")
 	addReaction(t, user4, issue1, comment1, "+1")
-	addReaction(t, ghost, issue1, comment1, "heart")
 
 	err := comment1.LoadReactions()
 	assert.NoError(t, err)
-	assert.Len(t, comment1.Reactions, 5)
+	assert.Len(t, comment1.Reactions, 4)
 
 	reactions := comment1.Reactions.GroupByType()
-	assert.Len(t, reactions["heart"], 4)
+	assert.Len(t, reactions["heart"], 3)
 	assert.Len(t, reactions["+1"], 1)
 }
 
@@ -160,7 +159,7 @@ func TestIssueCommentReactionCount(t *testing.T) {
 	comment1 := AssertExistsAndLoadBean(t, &Comment{ID: 1}).(*Comment)
 
 	addReaction(t, user1, issue1, comment1, "heart")
-	DeleteCommentReaction(user1, issue1, comment1, "heart")
+	assert.NoError(t, DeleteCommentReaction(user1, issue1, comment1, "heart"))
 
 	AssertNotExistsBean(t, &Reaction{Type: "heart", UserID: user1.ID, IssueID: issue1.ID, CommentID: comment1.ID})
 }