diff --git a/test/libcxx/test/config.py b/test/libcxx/test/config.py
index 897dd0c..0875fc1 100644
--- a/test/libcxx/test/config.py
+++ b/test/libcxx/test/config.py
@@ -538,6 +538,7 @@
                 '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER',
                 '-Wall', '-Wextra', '-Werror'
             ]
+            self.cxx.addWarningFlagIfSupported('-Wno-unused-command-line-argument')
             self.cxx.addWarningFlagIfSupported('-Wno-attributes')
             self.cxx.addWarningFlagIfSupported('-Wno-pessimizing-move')
             self.cxx.addWarningFlagIfSupported('-Wno-c++11-extensions')