diff --git a/src/hb-ot-cmap-table.hh b/src/hb-ot-cmap-table.hh
index fde57cd..a8747ee 100644
--- a/src/hb-ot-cmap-table.hh
+++ b/src/hb-ot-cmap-table.hh
@@ -714,7 +714,7 @@
       if (unlikely ((unsigned int) (gid + end - start) >= num_glyphs))
 	end = start + (hb_codepoint_t) num_glyphs - gid;
 
-      out->add_range (start, end);
+      out->add_range (start, hb_min (end, 0x10FFFFu));
     }
   }
 
@@ -883,7 +883,7 @@
       hb_codepoint_t first = arrayZ[i].startUnicodeValue;
       hb_codepoint_t last = hb_min ((hb_codepoint_t) (first + arrayZ[i].additionalCount),
 				    (hb_codepoint_t) HB_UNICODE_MAX);
-      out->add_range (first, last);
+      out->add_range (first, hb_min (last, 0x10FFFFu));
     }
   }