diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 88b902c525d7..16c0fcd6904a 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1354,6 +1354,11 @@ static void csi_m(struct vc_data *vc)
 		case 3:
 			vc->vc_italic = 1;
 			break;
+		case 21:
+			/*
+			 * No console drivers support double underline, so
+			 * convert it to a single underline.
+			 */
 		case 4:
 			vc->vc_underline = 1;
 			break;
@@ -1389,7 +1394,6 @@ static void csi_m(struct vc_data *vc)
 			vc->vc_disp_ctrl = 1;
 			vc->vc_toggle_meta = 1;
 			break;
-		case 21:
 		case 22:
 			vc->vc_intensity = 1;
 			break;