diff --git a/test/mutex_ctor_constexpr.cpp b/test/mutex_ctor_constexpr.cpp
index 6f20f3e40..eb8b1fc3a 100644
--- a/test/mutex_ctor_constexpr.cpp
+++ b/test/mutex_ctor_constexpr.cpp
@@ -22,4 +22,6 @@ constexpr NS::mutex m2{};
 int
 main(void)
   {
+    (void) m1;
+    (void) m2;
   }