diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp
index d05f6319d..41b14a6e5 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.array/delete_align_val_t_replace.pass.cpp
@@ -24,6 +24,11 @@
 // XFAIL: with_system_cxx_lib=macosx10.7
 // XFAIL: with_system_cxx_lib=macosx10.8
 
+// 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
+
 #include <new>
 #include <cstddef>
 #include <cstdlib>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t.pass.cpp
index f5e96e21c..4c9da4712 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t.pass.cpp
@@ -22,6 +22,12 @@
 // XFAIL: with_system_cxx_lib=macosx10.7
 // XFAIL: with_system_cxx_lib=macosx10.8
 
+
+// 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 link.
+// XFAIL: LIBCXX-WINDOWS-FIXME
+
 // test operator new
 
 #include <new>
@@ -36,7 +42,7 @@ constexpr auto OverAligned = alignof(std::max_align_t) * 2;
 
 int new_handler_called = 0;
 
-void new_handler()
+void my_new_handler()
 {
     ++new_handler_called;
     std::set_new_handler(0);
@@ -52,7 +58,7 @@ struct alignas(OverAligned) A
 
 void test_throw_max_size() {
 #ifndef TEST_HAS_NO_EXCEPTIONS
-    std::set_new_handler(new_handler);
+    std::set_new_handler(my_new_handler);
     try
     {
         void* vp = operator new[] (std::numeric_limits<std::size_t>::max(),
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow.pass.cpp
index 8176d0b91..8e9eff9e2 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow.pass.cpp
@@ -22,6 +22,11 @@
 // XFAIL: with_system_cxx_lib=macosx10.7
 // XFAIL: with_system_cxx_lib=macosx10.8
 
+// 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
+
 // test operator new (nothrow)
 
 #include <new>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow_replace.pass.cpp
index 6fbb40901..46f411d15 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_align_val_t_nothrow_replace.pass.cpp
@@ -19,6 +19,11 @@
 
 // XFAIL: no-aligned-allocation
 
+// 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.
+// XFAIL: LIBCXX-WINDOWS-FIXME
+
 // test operator new nothrow by replacing only operator new
 
 #include <new>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp
index 24a299074..514e5e104 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.single/delete_align_val_t_replace.pass.cpp
@@ -23,6 +23,11 @@
 // XFAIL: with_system_cxx_lib=macosx10.7
 // XFAIL: with_system_cxx_lib=macosx10.8
 
+// 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
+
 #include <new>
 #include <cstddef>
 #include <cstdlib>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t.pass.cpp
index 1196996e9..2dcb2dc2c 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t.pass.cpp
@@ -22,6 +22,11 @@
 // FIXME turn this into an XFAIL
 // UNSUPPORTED: no-aligned-allocation
 
+// 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
+
 // test operator new
 
 #include <new>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow.pass.cpp
index d3cc0be15..e77b41336 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow.pass.cpp
@@ -22,6 +22,11 @@
 // FIXME turn this into an XFAIL
 // UNSUPPORTED: no-aligned-allocation
 
+// 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
+
 // test operator new (nothrow)
 
 #include <new>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow_replace.pass.cpp
index 8031100cb..862ec1ba6 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_align_val_t_nothrow_replace.pass.cpp
@@ -19,6 +19,11 @@
 
 // XFAIL: no-aligned-allocation
 
+// 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.
+// XFAIL: LIBCXX-WINDOWS-FIXME
+
 // test operator new nothrow by replacing only operator new
 
 #include <new>