diff --git a/src/hb-ot-layout-common.hh b/src/hb-ot-layout-common.hh
index 87c0ae2f5..31e981341 100644
--- a/src/hb-ot-layout-common.hh
+++ b/src/hb-ot-layout-common.hh
@@ -3460,6 +3460,7 @@ struct VariationDevice
     if (!layout_variation_idx_delta_map->has (varIdx, &v))
       return_trace (nullptr);
 
+    c->start_zerocopy (this->static_size);
     auto *out = c->embed (this);
     if (unlikely (!out)) return_trace (nullptr);