diff --git a/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp b/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp
--- a/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp
+++ b/libcxx/test/std/utilities/template.bitset/bitset.members/to_ulong.pass.cpp
@@ -33,8 +33,9 @@
         std::min(max, max-1),
         max
     };
-    for (unsigned long j : tests) {
-         std::bitset<N> v(j);
+    for (std::size_t j_ : tests) {
+        unsigned long j = static_cast<unsigned long>(j_); // avoid compiler warnings
+        std::bitset<N> v(j);
         assert(j == v.to_ulong());
     }