diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1258,8 +1258,9 @@
 #  if defined(__clang__) && __has_attribute(acquire_capability)
 // Work around the attribute handling in clang.  When both __declspec and
 // __attribute__ are present, the processing goes awry preventing the definition
-// of the types.
-#    if !defined(_LIBCPP_OBJECT_FORMAT_COFF)
+// of the types. In MinGW mode, __declspec evaluates to __attribute__, and thus
+// combining the two does work.
+#    if !defined(_MSC_VER)
 #      define _LIBCPP_HAS_THREAD_SAFETY_ANNOTATIONS
 #    endif
 #  endif
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_guard.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_guard.pass.cpp
--- a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_guard.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_guard.pass.cpp
@@ -8,7 +8,7 @@
 
 // On Windows Clang bugs out when both __declspec and __attribute__ are present,
 // the processing goes awry preventing the definition of the types.
-// XFAIL: LIBCXX-WINDOWS-FIXME
+// XFAIL: msvc
 
 // UNSUPPORTED: libcpp-has-no-threads
 // REQUIRES: thread-safety
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_unlock.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_unlock.pass.cpp
--- a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_unlock.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_unlock.pass.cpp
@@ -8,7 +8,7 @@
 
 // On Windows Clang bugs out when both __declspec and __attribute__ are present,
 // the processing goes awry preventing the definition of the types.
-// XFAIL: LIBCXX-WINDOWS-FIXME
+// XFAIL: msvc
 
 // UNSUPPORTED: libcpp-has-no-threads
 // REQUIRES: thread-safety
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_missing_unlock.fail.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_missing_unlock.fail.cpp
--- a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_missing_unlock.fail.cpp
+++ b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_missing_unlock.fail.cpp
@@ -8,7 +8,7 @@
 
 // On Windows Clang bugs out when both __declspec and __attribute__ are present,
 // the processing goes awry preventing the definition of the types.
-// XFAIL: LIBCXX-WINDOWS-FIXME
+// XFAIL: msvc
 
 // UNSUPPORTED: libcpp-has-no-threads
 // REQUIRES: thread-safety
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_requires_capability.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_requires_capability.pass.cpp
--- a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_requires_capability.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_requires_capability.pass.cpp
@@ -8,7 +8,7 @@
 
 // On Windows Clang bugs out when both __declspec and __attribute__ are present,
 // the processing goes awry preventing the definition of the types.
-// XFAIL: LIBCXX-WINDOWS-FIXME
+// XFAIL: msvc
 
 // UNSUPPORTED: libcpp-has-no-threads
 // REQUIRES: thread-safety