diff --git a/src/hb-shape.cc b/src/hb-shape.cc
index 163a5bfb8..56c9046f8 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;
     }