diff --git a/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp
index f7a918607005..891b084dd32e 100644
--- a/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp
@@ -9,6 +9,9 @@
 //
 // UNSUPPORTED: libcpp-has-no-threads
 
+// This test uses the POSIX header <sys/time.h> which Windows doesn't provide
+// UNSUPPORTED: windows
+
 // This test depends on signal behaviour until r210210, so some system libs
 // don't pass.
 //