diff --git a/routers/web/auth/oauth.go b/routers/web/auth/oauth.go
index f44a102a49..9099aedb44 100644
--- a/routers/web/auth/oauth.go
+++ b/routers/web/auth/oauth.go
@@ -479,8 +479,7 @@ func AuthorizeOAuth(ctx *context.Context) {
 
 	// pkce support
 	switch form.CodeChallengeMethod {
-	case "S256":
-	case "plain":
+	case "S256", "plain":
 		if err := ctx.Session.Set("CodeChallengeMethod", form.CodeChallengeMethod); err != nil {
 			handleAuthorizeError(ctx, AuthorizeError{
 				ErrorCode:        ErrorCodeServerError,