diff --git a/src/hb-common.cc b/src/hb-common.cc
index a6a5144..d308f36 100644
--- a/src/hb-common.cc
+++ b/src/hb-common.cc
@@ -345,7 +345,7 @@
   hb_language_t language = (hb_language_t) hb_atomic_ptr_get (&default_language);
   if (unlikely (language == HB_LANGUAGE_INVALID)) {
     language = hb_language_from_string (setlocale (LC_CTYPE, NULL), -1);
-    hb_atomic_ptr_cmpexch (&default_language, HB_LANGUAGE_INVALID, language);
+    (void) hb_atomic_ptr_cmpexch (&default_language, HB_LANGUAGE_INVALID, language);
   }
 
   return default_language;
diff --git a/src/hb-icu.cc b/src/hb-icu.cc
index 86c8b5c..24cec9d 100644
--- a/src/hb-icu.cc
+++ b/src/hb-icu.cc
@@ -363,10 +363,8 @@
   if (!hb_atomic_ptr_get (&normalizer)) {
     UErrorCode icu_err = U_ZERO_ERROR;
     /* We ignore failure in getNFCInstace(). */
-    hb_atomic_ptr_cmpexch (&normalizer, NULL, unorm2_getNFCInstance (&icu_err));
+    (void) hb_atomic_ptr_cmpexch (&normalizer, NULL, unorm2_getNFCInstance (&icu_err));
   }
 #endif
   return const_cast<hb_unicode_funcs_t *> (&_hb_icu_unicode_funcs);
 }
-
-