diff --git a/test/libcxxabi/test/config.py b/test/libcxxabi/test/config.py
index c6982ad..6d4da90 100644
--- a/test/libcxxabi/test/config.py
+++ b/test/libcxxabi/test/config.py
@@ -48,6 +48,8 @@
         if not self.get_lit_bool('has_cxa_thread_atexit_impl', True):
             self.config.available_features.add(
                 'libcxxabi-no-cxa-thread-atexit-impl')
+        if not self.get_lit_bool('llvm_unwinder', False):
+            self.config.available_features.add('libcxxabi-has-system-unwinder')
 
     def configure_compile_flags(self):
         self.cxx.compile_flags += ['-DLIBCXXABI_NO_TIMER']
diff --git a/test/test_exception_address_alignment.pass.cpp b/test/test_exception_address_alignment.pass.cpp
index 5c5b4df..8e62944 100644
--- a/test/test_exception_address_alignment.pass.cpp
+++ b/test/test_exception_address_alignment.pass.cpp
@@ -7,13 +7,25 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: c++98, c++03
+
+// The system unwind.h on OS X provides an incorrectly aligned _Unwind_Exception
+// type. That causes these tests to fail. This XFAIL is my best attempt at
+// working around this failure.
+// XFAIL: darwin && libcxxabi-has-system-unwinder
+
 // Test that the address of the exception object is properly aligned to the
 // largest supported alignment for the system.
 
 #include <cstdint>
 #include <cassert>
 
+#include <unwind.h>
+
 struct __attribute__((aligned)) AlignedType {};
+static_assert(alignof(AlignedType) == alignof(_Unwind_Exception),
+  "_Unwind_Exception is incorrectly aligned. This test is expected to fail");
+
 struct MinAligned {  };
 static_assert(alignof(MinAligned) == 1 && sizeof(MinAligned) == 1, "");