diff --git a/src/hb-common.cc b/src/hb-common.cc
index cb1fb43ffbbaf307ed5cd6ec0e0f38d0b24d73ce..1d0e7264234b9fef4ff1890fce0eb3c3aba50ede 100644
--- a/src/hb-common.cc
+++ b/src/hb-common.cc
@@ -524,6 +524,7 @@ hb_script_get_horizontal_direction (hb_script_t script)
     case HB_SCRIPT_PSALTER_PAHLAVI:
 
     /* Unicode-8.0 additions */
+    case HB_SCRIPT_HATRAN:
     case HB_SCRIPT_OLD_HUNGARIAN:
 
     /* Unicode-9.0 additions */