diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -381,6 +381,9 @@
   let ObjectFormats = ["ELF"];
 }
 
+def ExcludeTarget : TargetSpec {
+  let CustomCode = [{ !Target.getTriple().isOSzOS() }];
+}
 // Attribute subject match rules that are used for #pragma clang attribute.
 //
 // A instance of AttrSubjectMatcherRule represents an individual match rule.
@@ -2221,7 +2224,7 @@
   let Documentation = [Undocumented];
 }
 
-def InitPriority : InheritableAttr {
+def InitPriority : InheritableAttr, TargetSpecificAttr<ExcludeTarget> {
   let Spellings = [GCC<"init_priority", /*AllowInC*/0>];
   let Args = [UnsignedArgument<"Priority">];
   let Subjects = SubjectList<[Var], ErrorDiag>;
diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1435,6 +1435,12 @@
 #define _LIBCPP_HAS_NO_FGETPOS_FSETPOS
 #endif
 
+#if __has_attribute(init_priority)
+# define _LIBCPP_INIT_PRIORITY_MAX __attribute__((init_priority(101)))
+#else
+# define _LIBCPP_INIT_PRIORITY_MAX
+#endif
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG
diff --git a/libcxx/include/experimental/__config b/libcxx/include/experimental/__config
--- a/libcxx/include/experimental/__config
+++ b/libcxx/include/experimental/__config
@@ -76,4 +76,14 @@
 #define _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES 16
 #endif
 
+// Detect if the init_priority attribute is supported.
+#if (defined(_LIBCPP_COMPILER_GCC) && defined(__APPLE__)) \
+  || defined(_LIBCPP_COMPILER_MSVC) || defined(__MVS__)
+// GCC on Apple doesn't support the init priority
+// attribute, same for MSVC and z/OS.
+# define _LIBCPP_INIT_PRIORITY_MAX
+#else
+# define _LIBCPP_INIT_PRIORITY_MAX __attribute__((init_priority(101)))
+#endif
+
 #endif
diff --git a/libcxx/src/experimental/memory_resource.cpp b/libcxx/src/experimental/memory_resource.cpp
--- a/libcxx/src/experimental/memory_resource.cpp
+++ b/libcxx/src/experimental/memory_resource.cpp
@@ -76,16 +76,6 @@
   ~ResourceInitHelper() {}
 };
 
-// Detect if the init_priority attribute is supported.
-#if (defined(_LIBCPP_COMPILER_GCC) && defined(__APPLE__)) \
-  || defined(_LIBCPP_COMPILER_MSVC)
-// GCC on Apple doesn't support the init priority attribute,
-// and MSVC doesn't support any GCC attributes.
-# define _LIBCPP_INIT_PRIORITY_MAX
-#else
-# define _LIBCPP_INIT_PRIORITY_MAX __attribute__((init_priority(101)))
-#endif
-
 // When compiled in C++14 this initialization should be a constant expression.
 // Only in C++11 is "init_priority" needed to ensure initialization order.
 #if _LIBCPP_STD_VER > 11
diff --git a/libcxx/src/iostream.cpp b/libcxx/src/iostream.cpp
--- a/libcxx/src/iostream.cpp
+++ b/libcxx/src/iostream.cpp
@@ -77,7 +77,7 @@
 #endif
 ;
 
-_LIBCPP_HIDDEN ios_base::Init __start_std_streams __attribute__((init_priority(101)));
+_LIBCPP_HIDDEN ios_base::Init __start_std_streams _LIBCPP_INIT_PRIORITY_MAX;
 
 // On Windows the TLS storage for locales needs to be initialized before we create
 // the standard streams, otherwise it may not be alive during program termination