Index: libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.temp_dir_path/temp_directory_path.pass.cpp
===================================================================
--- libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.temp_dir_path/temp_directory_path.pass.cpp
+++ libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.temp_dir_path/temp_directory_path.pass.cpp
@@ -26,11 +26,19 @@
 using namespace fs;
 
 void PutEnv(std::string var, fs::path value) {
+#ifdef _WIN32
+    assert(::_putenv((var + "=" + value.string()).c_str()) == 0);
+#else
     assert(::setenv(var.c_str(), value.string().c_str(), /* overwrite */ 1) == 0);
+#endif
 }
 
 void UnsetEnv(std::string var) {
+#ifdef _WIN32
+    assert(::_putenv((var + "=").c_str()) == 0);
+#else
     assert(::unsetenv(var.c_str()) == 0);
+#endif
 }
 
 TEST_SUITE(filesystem_temp_directory_path_test_suite)