diff --git a/src/hb-ot-cmap-table.hh b/src/hb-ot-cmap-table.hh
index fd96a2758..b9d3aaa69 100644
--- a/src/hb-ot-cmap-table.hh
+++ b/src/hb-ot-cmap-table.hh
@@ -99,8 +99,8 @@ struct CmapSubtableFormat4
 	   hb_requires (hb_is_iterator (Iterator))>
   void to_ranges (Iterator it, Writer& range_writer)
   {
-    hb_codepoint_t start_cp, prev_run_start_cp, run_start_cp, end_cp, last_gid;
-    int run_length, delta, prev_delta;
+    hb_codepoint_t start_cp, prev_run_start_cp, run_start_cp, end_cp, last_gid = 0;
+    int run_length, delta, prev_delta = 0;
 
     enum {
       FIRST_SUB_RANGE,