diff --git a/libcxx/test/libcxx/debug/extern-templates.sh.cpp b/libcxx/test/libcxx/debug/extern-templates.sh.cpp
--- a/libcxx/test/libcxx/debug/extern-templates.sh.cpp
+++ b/libcxx/test/libcxx/debug/extern-templates.sh.cpp
@@ -14,7 +14,12 @@
 // UNSUPPORTED: libcxx-no-debug-mode
 // UNSUPPORTED: libcpp-has-no-localization
 
-// XFAIL: LIBCXX-WINDOWS-FIXME
+// This test relies on linking a shared library and then passing that shared
+// library as input when linking an executable; this is generally not supported
+// on Windows (GNU ld supports it, but MS link.exe and LLD don't) - one has to
+// use an import library instead. (Additionally, the test uses the -fPIC
+// option which clang doesn't accept on Windows.)
+// UNSUPPORTED: windows
 
 // RUN: %{cxx} %{flags} %{compile_flags} %s %{link_flags} -fPIC -DTU1 -D_LIBCPP_DEBUG=1 -fvisibility=hidden -shared -o %t.lib
 // RUN: cd %T && %{cxx} %{flags} %{compile_flags} %s ./%basename_t.tmp.lib %{link_flags} -fPIC -DTU2 -D_LIBCPP_DEBUG=1 -fvisibility=hidden -o %t.exe