diff --git a/libcxx/src/filesystem/operations.cpp b/libcxx/src/filesystem/operations.cpp
--- a/libcxx/src/filesystem/operations.cpp
+++ b/libcxx/src/filesystem/operations.cpp
@@ -42,6 +42,10 @@
 # pragma comment(lib, "rt")
 #endif
 
+#if defined(__MVS__) && !defined(PATH_MAX)
+#define PATH_MAX _XOPEN_PATH_MAX
+#endif
+
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
 namespace {