diff --git a/services/mirror/mirror.go b/services/mirror/mirror.go
index 22aed2c3a480..fc494bfce285 100644
--- a/services/mirror/mirror.go
+++ b/services/mirror/mirror.go
@@ -303,8 +303,8 @@ func runSync(m *models.Mirror) ([]*mirrorSyncResult, bool) {
 		return nil, false
 	}
 
-	for i := range branches {
-		cache.Remove(m.Repo.GetCommitsCountCacheKey(branches[i].Name, true))
+	for _, branch := range branches {
+		cache.Remove(m.Repo.GetCommitsCountCacheKey(branch.Name, true))
 	}
 
 	m.UpdatedUnix = timeutil.TimeStampNow()
@@ -422,6 +422,10 @@ func syncMirror(repoID string) {
 			return
 		}
 		defer gitRepo.Close()
+
+		if ok := checkAndUpdateEmptyRepository(m, gitRepo, results); !ok {
+			return
+		}
 	}
 
 	for _, result := range results {
@@ -487,6 +491,67 @@ func syncMirror(repoID string) {
 	log.Trace("SyncMirrors [repo: %-v]: Successfully updated", m.Repo)
 }
 
+func checkAndUpdateEmptyRepository(m *models.Mirror, gitRepo *git.Repository, results []*mirrorSyncResult) bool {
+	if !m.Repo.IsEmpty {
+		return true
+	}
+
+	hasDefault := false
+	hasMaster := false
+	defaultBranchName := m.Repo.DefaultBranch
+	if len(defaultBranchName) == 0 {
+		defaultBranchName = setting.Repository.DefaultBranch
+	}
+	firstName := ""
+	for _, result := range results {
+		if strings.HasPrefix(result.refName, "refs/pull/") {
+			continue
+		}
+		tp, name := git.SplitRefName(result.refName)
+		if len(tp) > 0 && tp != git.BranchPrefix {
+			continue
+		}
+		if len(firstName) == 0 {
+			firstName = name
+		}
+
+		hasDefault = hasDefault || name == defaultBranchName
+		hasMaster = hasMaster || name == "master"
+	}
+
+	if len(firstName) > 0 {
+		if hasDefault {
+			m.Repo.DefaultBranch = defaultBranchName
+		} else if hasMaster {
+			m.Repo.DefaultBranch = "master"
+		} else {
+			m.Repo.DefaultBranch = firstName
+		}
+		// Update the git repository default branch
+		if err := gitRepo.SetDefaultBranch(m.Repo.DefaultBranch); err != nil {
+			if !git.IsErrUnsupportedVersion(err) {
+				log.Error("Failed to update default branch of underlying git repository %-v. Error: %v", m.Repo, err)
+				desc := fmt.Sprintf("Failed to uupdate default branch of underlying git repository '%s': %v", m.Repo.RepoPath(), err)
+				if err = models.CreateRepositoryNotice(desc); err != nil {
+					log.Error("CreateRepositoryNotice: %v", err)
+				}
+				return false
+			}
+		}
+		m.Repo.IsEmpty = false
+		// Update the is empty and default_branch columns
+		if err := models.UpdateRepositoryCols(m.Repo, "default_branch", "is_empty"); err != nil {
+			log.Error("Failed to update default branch of repository %-v. Error: %v", m.Repo, err)
+			desc := fmt.Sprintf("Failed to uupdate default branch of repository '%s': %v", m.Repo.RepoPath(), err)
+			if err = models.CreateRepositoryNotice(desc); err != nil {
+				log.Error("CreateRepositoryNotice: %v", err)
+			}
+			return false
+		}
+	}
+	return true
+}
+
 // InitSyncMirrors initializes a go routine to sync the mirrors
 func InitSyncMirrors() {
 	go graceful.GetManager().RunWithShutdownContext(SyncMirrors)