diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 6487cb7ba..15a43b2d6 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -3054,6 +3054,7 @@ struct GSUBGPOS
 			      unsigned int *index) const
   {
 #ifdef HB_NO_VAR
+    *index = NOT_FOUND_INDEX;
     return false;
 #endif
     return (version.to_int () >= 0x00010001u ? this+featureVars : Null (FeatureVariations))