diff --git a/third_party/libcxxabi/test/BUILD.mk b/third_party/libcxxabi/test/BUILD.mk
index 2365b6cc0..42c58e6f8 100644
--- a/third_party/libcxxabi/test/BUILD.mk
+++ b/third_party/libcxxabi/test/BUILD.mk
@@ -41,7 +41,6 @@ THIRD_PARTY_LIBCXXABI_TEST_SRCS =					\
 	third_party/libcxxabi/test/exception_object_alignment.pass.cc	\
 	third_party/libcxxabi/test/exception_object_alignment.2.pass.cc	\
 	third_party/libcxxabi/test/guard_test_basic.pass.cc		\
-	third_party/libcxxabi/test/guard_threaded_test.pass.cc		\
 	third_party/libcxxabi/test/incomplete_type.sh.cc		\
 	third_party/libcxxabi/test/inherited_exception.pass.cc		\
 	third_party/libcxxabi/test/test_aux_runtime.pass.cc		\
@@ -64,6 +63,10 @@ THIRD_PARTY_LIBCXXABI_TEST_SRCS =					\
 	third_party/libcxxabi/test/unwind_05.pass.cc			\
 	third_party/libcxxabi/test/unwind_06.pass.cc
 
+# TODO: LLVM needs to finish the code that lets us use NSYNC futexes
+THIRD_PARTY_LIBCXXABI_TEST_SRCS_TOOSLOW_COSMO =				\
+	third_party/libcxxabi/test/guard_threaded_test.pass.cc		\
+
 # TODO: Add this test when #1073 is fixed
 THIRD_PARTY_LIBCXXABI_TEST_SRCS_FAILING_COSMO =				\
 	third_party/libcxxabi/test/thread_local_destruction_order.pass.cc