diff --git a/src/hb-ot-var-hvar-table.hh b/src/hb-ot-var-hvar-table.hh
index bf2c1c165..2b937e72f 100644
--- a/src/hb-ot-var-hvar-table.hh
+++ b/src/hb-ot-var-hvar-table.hh
@@ -182,6 +182,7 @@ struct index_map_subset_plan_t
       last_gid = gid;
     }
 
+    if (last_gid == (hb_codepoint_t)-1) return;
     map_count = last_gid;
     for (gid = 0; gid < map_count; gid++)
     {