diff --git a/src/hb-shape.cc b/src/hb-shape.cc
index 163a5bfb80336b774bb0aa905ba9953d12c3bbef..56c9046f83443690a223b27bf30a65877e17bcb5 100644
--- a/src/hb-shape.cc
+++ b/src/hb-shape.cc
@@ -87,7 +87,7 @@ retry:
   {
     char *env = getenv ("HB_SHAPER_LIST");
     if (!env || !*env) {
-      hb_atomic_ptr_cmpexch (&static_shapers, NULL, (const hb_shaper_pair_t *) all_shapers);
+      (void) hb_atomic_ptr_cmpexch (&static_shapers, NULL, (const hb_shaper_pair_t *) all_shapers);
       return (const hb_shaper_pair_t *) all_shapers;
     }