diff --git a/services/pull/check.go b/services/pull/check.go
index c877cc84e..ea91f3a86 100644
--- a/services/pull/check.go
+++ b/services/pull/check.go
@@ -61,7 +61,7 @@ func checkAndUpdateStatus(pr *models.PullRequest) {
 	}
 
 	if !has {
-		if err := pr.UpdateCols("merge_base", "status", "conflicted_files"); err != nil {
+		if err := pr.UpdateColsIfNotMerged("merge_base", "status", "conflicted_files"); err != nil {
 			log.Error("Update[%d]: %v", pr.ID, err)
 		}
 	}
diff --git a/services/pull/pull.go b/services/pull/pull.go
index 5c7ec91f5..ce5c4ff22 100644
--- a/services/pull/pull.go
+++ b/services/pull/pull.go
@@ -120,7 +120,7 @@ func ChangeTargetBranch(pr *models.PullRequest, doer *models.User, targetBranch
 	if pr.Status == models.PullRequestStatusChecking {
 		pr.Status = models.PullRequestStatusMergeable
 	}
-	if err := pr.UpdateCols("status, conflicted_files, base_branch"); err != nil {
+	if err := pr.UpdateColsIfNotMerged("merge_base", "status", "conflicted_files", "base_branch"); err != nil {
 		return err
 	}