diff --git a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp
--- a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp
+++ b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp
@@ -18,12 +18,6 @@
 // However, support for that was broken prior to Clang 8 and AppleClang 11.
 // UNSUPPORTED: apple-clang-9, apple-clang-10
 // UNSUPPORTED: clang-5, clang-6, clang-7
-// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13}}
-
-// On Windows libc++ doesn't provide its own definitions for new/delete
-// but instead depends on the ones in VCRuntime. However VCRuntime does not
-// yet provide aligned new/delete definitions so this test fails to compile/link.
-// XFAIL: LIBCXX-WINDOWS-FIXME
 
 // Libcxx when built for z/OS doesn't contain the aligned allocation functions,
 // nor does the dynamic library shipped with z/OS.
@@ -48,22 +42,29 @@
     aligned_delete_called = 0;
 }
 
-void operator delete(void* p) TEST_NOEXCEPT
+alignas(OverAligned) char DummyData[OverAligned * 4];
+
+void* operator new [] (std::size_t s, std::align_val_t)
+{
+    assert(s <= sizeof(DummyData));
+    return DummyData;
+}
+
+void operator delete [] (void* p) noexcept
 {
     ++unsized_delete_called;
     std::free(p);
 }
 
-void operator delete(void* p, const std::nothrow_t&) TEST_NOEXCEPT
+void operator delete [] (void* p, const std::nothrow_t&) noexcept
 {
     ++unsized_delete_nothrow_called;
     std::free(p);
 }
 
-void operator delete [] (void* p, std::align_val_t) TEST_NOEXCEPT
+void operator delete [] (void*, std::align_val_t) noexcept
 {
     ++aligned_delete_called;
-    std::free(p);
 }
 
 struct alignas(OverAligned) A {};
diff --git a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp
--- a/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp
+++ b/libcxx/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp
@@ -18,12 +18,6 @@
 // However, support for that was broken prior to Clang 8 and AppleClang 11.
 // UNSUPPORTED: apple-clang-9, apple-clang-10
 // UNSUPPORTED: clang-5, clang-6, clang-7
-// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13}}
-
-// On Windows libc++ doesn't provide its own definitions for new/delete
-// but instead depends on the ones in VCRuntime. However VCRuntime does not
-// yet provide aligned new/delete definitions so this test fails to compile/link.
-// XFAIL: LIBCXX-WINDOWS-FIXME
 
 // Libcxx when built for z/OS doesn't contain the aligned allocation functions,
 // nor does the dynamic library shipped with z/OS.
@@ -48,22 +42,29 @@
     aligned_delete_called = 0;
 }
 
-void operator delete(void* p) TEST_NOEXCEPT
+alignas(OverAligned) char DummyData[OverAligned * 4];
+
+void* operator new (std::size_t s, std::align_val_t)
+{
+    assert(s <= sizeof(DummyData));
+    return DummyData;
+}
+
+void operator delete(void* p) noexcept
 {
     ++unsized_delete_called;
     std::free(p);
 }
 
-void operator delete(void* p, const std::nothrow_t&) TEST_NOEXCEPT
+void operator delete(void* p, const std::nothrow_t&) noexcept
 {
     ++unsized_delete_nothrow_called;
     std::free(p);
 }
 
-void operator delete(void* p, std::align_val_t) TEST_NOEXCEPT
+void operator delete(void*, std::align_val_t) noexcept
 {
     ++aligned_delete_called;
-    std::free(p);
 }
 
 struct alignas(OverAligned) A {};