diff --git a/src/hb-ot-var-gvar-table.hh b/src/hb-ot-var-gvar-table.hh
index 322a261b3..982c5c4a9 100644
--- a/src/hb-ot-var-gvar-table.hh
+++ b/src/hb-ot-var-gvar-table.hh
@@ -360,7 +360,7 @@ struct GlyphVariationData
 	  deltas.arrayZ[i] = * (const HBINT8 *) p++;
 	}
       }
-      if (j < run_count)
+      if (unlikely (j < run_count))
 	return false;
     }
     return true;