diff --git a/libstdc++-v3/testsuite/29_atomics/atomic_ref/requirements_neg.cc b/libstdc++-v3/testsuite/29_atomics/atomic_ref/requirements_neg.cc
index 8b0abbde023..a3613e0e733 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic_ref/requirements_neg.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic_ref/requirements_neg.cc
@@ -2,6 +2,8 @@
 
 #include <atomic>
 
+using std::size_t;
+
 template<size_t N>
 struct NonTrivial
 {