diff --git a/src/hb-ot-layout-common-private.hh b/src/hb-ot-layout-common-private.hh
index 86224a15e..2f6e80468 100644
--- a/src/hb-ot-layout-common-private.hh
+++ b/src/hb-ot-layout-common-private.hh
@@ -1014,7 +1014,7 @@ struct ClassDefFormat2
     if (klass == 0)
     {
       /* Match if there's any glyph that is not listed! */
-      hb_codepoint_t g = -1;
+      hb_codepoint_t g = (hb_codepoint_t) -1;
       for (unsigned int i = 0; i < count; i++)
       {
 	if (!hb_set_next (glyphs, &g))
@@ -1023,7 +1023,7 @@ struct ClassDefFormat2
 	  return true;
 	g = rangeRecord[i].end;
       }
-      if (g != -1 && hb_set_next (glyphs, &g))
+      if (g != (hb_codepoint_t) -1 && hb_set_next (glyphs, &g))
         return true;
       /* Fall through. */
     }