diff --git a/routers/api/v1/repo/pull.go b/routers/api/v1/repo/pull.go
index 502adb18b6..5a5acc3c69 100644
--- a/routers/api/v1/repo/pull.go
+++ b/routers/api/v1/repo/pull.go
@@ -955,7 +955,7 @@ func MergePullRequest(ctx *context.APIContext) {
 	if manuallyMerged {
 		if err := pull_service.MergedManually(ctx, pr, ctx.Doer, ctx.Repo.GitRepo, form.MergeCommitID); err != nil {
 			if models.IsErrInvalidMergeStyle(err) {
-				ctx.Error(http.StatusMethodNotAllowed, "Invalid merge style", fmt.Errorf("%s is not allowed an allowed merge style for this repository", repo_model.MergeStyle(form.Do)))
+				ctx.Error(http.StatusMethodNotAllowed, "Invalid merge style", fmt.Errorf("%s is not an allowed merge style for this repository", repo_model.MergeStyle(form.Do)))
 				return
 			}
 			if strings.Contains(err.Error(), "Wrong commit ID") {
@@ -1005,7 +1005,7 @@ func MergePullRequest(ctx *context.APIContext) {
 
 	if err := pull_service.Merge(ctx, pr, ctx.Doer, ctx.Repo.GitRepo, repo_model.MergeStyle(form.Do), form.HeadCommitID, message, false); err != nil {
 		if models.IsErrInvalidMergeStyle(err) {
-			ctx.Error(http.StatusMethodNotAllowed, "Invalid merge style", fmt.Errorf("%s is not allowed an allowed merge style for this repository", repo_model.MergeStyle(form.Do)))
+			ctx.Error(http.StatusMethodNotAllowed, "Invalid merge style", fmt.Errorf("%s is not an allowed merge style for this repository", repo_model.MergeStyle(form.Do)))
 		} else if models.IsErrMergeConflicts(err) {
 			conflictError := err.(models.ErrMergeConflicts)
 			ctx.JSON(http.StatusConflict, conflictError)