diff --git a/models/repo/fork.go b/models/repo/fork.go
index 1c75e86458..b13b7b02ef 100644
--- a/models/repo/fork.go
+++ b/models/repo/fork.go
@@ -21,15 +21,17 @@ func GetRepositoriesByForkID(ctx context.Context, forkID int64) ([]*Repository,
 }
 
 // GetForkedRepo checks if given user has already forked a repository with given ID.
-func GetForkedRepo(ctx context.Context, ownerID, repoID int64) *Repository {
+func GetForkedRepo(ctx context.Context, ownerID, repoID int64) (*Repository, error) {
 	repo := new(Repository)
-	has, _ := db.GetEngine(ctx).
+	has, err := db.GetEngine(ctx).
 		Where("owner_id=? AND fork_id=?", ownerID, repoID).
 		Get(repo)
-	if has {
-		return repo
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, ErrRepoNotExist{ID: repoID}
 	}
-	return nil
+	return repo, nil
 }
 
 // HasForkedRepo checks if given user has already forked a repository with given ID.
@@ -41,19 +43,6 @@ func HasForkedRepo(ctx context.Context, ownerID, repoID int64) bool {
 	return has
 }
 
-// GetUserFork return user forked repository from this repository, if not forked return nil
-func GetUserFork(ctx context.Context, repoID, userID int64) (*Repository, error) {
-	var forkedRepo Repository
-	has, err := db.GetEngine(ctx).Where("fork_id = ?", repoID).And("owner_id = ?", userID).Get(&forkedRepo)
-	if err != nil {
-		return nil, err
-	}
-	if !has {
-		return nil, nil
-	}
-	return &forkedRepo, nil
-}
-
 // IncrementRepoForkNum increment repository fork number
 func IncrementRepoForkNum(ctx context.Context, repoID int64) error {
 	_, err := db.GetEngine(ctx).Exec("UPDATE `repository` SET num_forks=num_forks+1 WHERE id=?", repoID)
@@ -87,8 +76,8 @@ func GetForksByUserAndOrgs(ctx context.Context, user *user_model.User, repo *Rep
 	if user == nil {
 		return repoList, nil
 	}
-	forkedRepo, err := GetUserFork(ctx, repo.ID, user.ID)
-	if err != nil {
+	forkedRepo, err := GetForkedRepo(ctx, user.ID, repo.ID)
+	if err != nil && !IsErrRepoNotExist(err) {
 		return repoList, err
 	}
 	if forkedRepo != nil {
diff --git a/models/repo/fork_test.go b/models/repo/fork_test.go
index e8dca204cc..4004c977a2 100644
--- a/models/repo/fork_test.go
+++ b/models/repo/fork_test.go
@@ -13,21 +13,22 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestGetUserFork(t *testing.T) {
+func Test_GetForkedRepo(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
 	// User13 has repo 11 forked from repo10
 	repo, err := repo_model.GetRepositoryByID(db.DefaultContext, 10)
 	assert.NoError(t, err)
 	assert.NotNil(t, repo)
-	repo, err = repo_model.GetUserFork(db.DefaultContext, repo.ID, 13)
+	repo, err = repo_model.GetForkedRepo(db.DefaultContext, 13, repo.ID)
 	assert.NoError(t, err)
 	assert.NotNil(t, repo)
 
 	repo, err = repo_model.GetRepositoryByID(db.DefaultContext, 9)
 	assert.NoError(t, err)
 	assert.NotNil(t, repo)
-	repo, err = repo_model.GetUserFork(db.DefaultContext, repo.ID, 13)
-	assert.NoError(t, err)
+	repo, err = repo_model.GetForkedRepo(db.DefaultContext, 13, repo.ID)
+	assert.Error(t, err)
+	assert.True(t, repo_model.IsErrRepoNotExist(err))
 	assert.Nil(t, repo)
 }
diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
index d0c3459b63..d212f7ff3e 100644
--- a/routers/api/v1/repo/pull.go
+++ b/routers/api/v1/repo/pull.go
@@ -1113,7 +1113,11 @@ func parseCompareInfo(ctx *context.APIContext, form api.CreatePullRequestOption)
 	isSameRepo := ctx.Repo.Owner.ID == headUser.ID
 
 	// Check if current user has fork of repository or in the same repository.
-	headRepo := repo_model.GetForkedRepo(ctx, headUser.ID, baseRepo.ID)
+	headRepo, err := repo_model.GetForkedRepo(ctx, headUser.ID, baseRepo.ID)
+	if err != nil && !repo_model.IsErrRepoNotExist(err) {
+		ctx.Error(http.StatusInternalServerError, "GetForkedRepo", err)
+		return nil, nil
+	}
 	if headRepo == nil && !isSameRepo {
 		err = baseRepo.GetBaseRepo(ctx)
 		if err != nil {
diff --git a/routers/web/repo/compare.go b/routers/web/repo/compare.go
index b3c1eb7cb0..b037c438e9 100644
--- a/routers/web/repo/compare.go
+++ b/routers/web/repo/compare.go
@@ -357,7 +357,11 @@ func ParseCompareInfo(ctx *context.Context) *common.CompareInfo {
 	// "OwnForkRepo"
 	var ownForkRepo *repo_model.Repository
 	if ctx.Doer != nil && baseRepo.OwnerID != ctx.Doer.ID {
-		repo := repo_model.GetForkedRepo(ctx, ctx.Doer.ID, baseRepo.ID)
+		repo, err := repo_model.GetForkedRepo(ctx, ctx.Doer.ID, baseRepo.ID)
+		if err != nil && !repo_model.IsErrRepoNotExist(err) {
+			ctx.ServerError("GetForkedRepo", err)
+			return nil
+		}
 		if repo != nil {
 			ownForkRepo = repo
 			ctx.Data["OwnForkRepo"] = ownForkRepo
@@ -381,13 +385,21 @@ func ParseCompareInfo(ctx *context.Context) *common.CompareInfo {
 
 	// 5. If the headOwner has a fork of the baseRepo - use that
 	if !has {
-		ci.HeadRepo = repo_model.GetForkedRepo(ctx, ci.HeadUser.ID, baseRepo.ID)
+		ci.HeadRepo, err = repo_model.GetForkedRepo(ctx, ci.HeadUser.ID, baseRepo.ID)
+		if err != nil && !repo_model.IsErrRepoNotExist(err) {
+			ctx.ServerError("GetForkedRepo", err)
+			return nil
+		}
 		has = ci.HeadRepo != nil
 	}
 
 	// 6. If the baseRepo is a fork and the headUser has a fork of that use that
 	if !has && baseRepo.IsFork {
-		ci.HeadRepo = repo_model.GetForkedRepo(ctx, ci.HeadUser.ID, baseRepo.ForkID)
+		ci.HeadRepo, err = repo_model.GetForkedRepo(ctx, ci.HeadUser.ID, baseRepo.ForkID)
+		if err != nil && !repo_model.IsErrRepoNotExist(err) {
+			ctx.ServerError("GetForkedRepo", err)
+			return nil
+		}
 		has = ci.HeadRepo != nil
 	}
 
diff --git a/routers/web/repo/fork.go b/routers/web/repo/fork.go
index 786b5d7e43..e4f8ea517a 100644
--- a/routers/web/repo/fork.go
+++ b/routers/web/repo/fork.go
@@ -167,7 +167,11 @@ func ForkPost(ctx *context.Context) {
 			ctx.RenderWithErr(ctx.Tr("repo.settings.new_owner_has_same_repo"), tplFork, &form)
 			return
 		}
-		repo := repo_model.GetForkedRepo(ctx, ctxUser.ID, traverseParentRepo.ID)
+		repo, err := repo_model.GetForkedRepo(ctx, ctxUser.ID, traverseParentRepo.ID)
+		if err != nil && !repo_model.IsErrRepoNotExist(err) {
+			ctx.ServerError("GetForkedRepo", err)
+			return
+		}
 		if repo != nil {
 			ctx.Redirect(ctxUser.HomeLink() + "/" + url.PathEscape(repo.Name))
 			return
diff --git a/services/repository/fork.go b/services/repository/fork.go
index cff0b1a403..53fe036628 100644
--- a/services/repository/fork.go
+++ b/services/repository/fork.go
@@ -71,8 +71,8 @@ func ForkRepository(ctx context.Context, doer, owner *user_model.User, opts Fork
 		}
 	}
 
-	forkedRepo, err := repo_model.GetUserFork(ctx, opts.BaseRepo.ID, owner.ID)
-	if err != nil {
+	forkedRepo, err := repo_model.GetForkedRepo(ctx, owner.ID, opts.BaseRepo.ID)
+	if err != nil && !repo_model.IsErrRepoNotExist(err) {
 		return nil, err
 	}
 	if forkedRepo != nil {