diff --git a/src/hb-common.cc b/src/hb-common.cc
index 6093289f5..170b75f31 100644
--- a/src/hb-common.cc
+++ b/src/hb-common.cc
@@ -274,10 +274,16 @@ hb_script_get_horizontal_direction (hb_script_t script)
     /* Unicode-4.0 additions */
     case HB_SCRIPT_CYPRIOT:
 
+    /* Unicode-4.1 additions */
+    case HB_SCRIPT_KHAROSHTHI:
+
     /* Unicode-5.0 additions */
     case HB_SCRIPT_PHOENICIAN:
     case HB_SCRIPT_NKO:
 
+    /* Unicode-5.1 additions */
+    case HB_SCRIPT_LYDIAN:
+
     /* Unicode-5.2 additions */
     case HB_SCRIPT_AVESTAN:
     case HB_SCRIPT_IMPERIAL_ARAMAIC: