diff --git a/winsup/cygwin/errno.cc b/winsup/cygwin/errno.cc
index 420326566..55219cccc 100644
--- a/winsup/cygwin/errno.cc
+++ b/winsup/cygwin/errno.cc
@@ -53,6 +53,7 @@ static const errmap_t errmap[] =
   X (CALL_NOT_IMPLEMENTED,	ENOSYS),
   X (CANCELLED,			EINTR),
   X (CANNOT_MAKE,		EPERM),
+  X (CASE_DIFFERING_NAMES_IN_DIR, EINVAL),
   X (CHILD_NOT_COMPLETE,	EBUSY),
   X (COMMITMENT_LIMIT,		EAGAIN),
   X (CONNECTION_REFUSED,	ECONNREFUSED),
diff --git a/winsup/cygwin/fhandler_disk_file.cc b/winsup/cygwin/fhandler_disk_file.cc
index 26726c5d7..3cec1ed84 100644
--- a/winsup/cygwin/fhandler_disk_file.cc
+++ b/winsup/cygwin/fhandler_disk_file.cc
@@ -2547,15 +2547,7 @@ fhandler_disk_file::fs_ioc_setflags (uint64_t flags)
 					 FileCaseSensitiveInformation);
 	  if (!NT_SUCCESS (status))
 	    {
-	      /* Special case: The directory contains files which only
-		 differ in case.  NtSetInformationFile refuses to change
-		 back to case insensitivity and returns status 0xc00004b3.
-		 There's no STATUS_xyz macro assigned to that value yet,
-		 nor does it map to a useful Win32 error value. */
-	      if (status == (NTSTATUS) 0xc00004b3)
-		set_errno (EINVAL);	/* Does that make sense? */
-	      else
-		__seterrno_from_nt_status (status);
+	      __seterrno_from_nt_status (status);
 	      goto out;
 	    }
 	}
diff --git a/winsup/cygwin/ntdll.h b/winsup/cygwin/ntdll.h
index f7c427e40..59c396676 100644
--- a/winsup/cygwin/ntdll.h
+++ b/winsup/cygwin/ntdll.h
@@ -15,6 +15,11 @@
 extern GUID __cygwin_socket_guid;
 #define CYGWIN_SOCKET_GUID (&__cygwin_socket_guid)
 
+/* Status codes not known to Mingw-w64 yet.  The error code needs to
+   be maintained here as well as long as Mingw-w64 didn't follow up. */
+#define STATUS_CASE_DIFFERING_NAMES_IN_DIR	((NTSTATUS)0xC00004B3)
+#define ERROR_CASE_DIFFERING_NAMES_IN_DIR	__MSABI_LONG(424)
+
 /* Custom Cygwin-only status codes. */
 #define STATUS_THREAD_SIGNALED	((NTSTATUS)0xe0000001)
 #define STATUS_THREAD_CANCELED	((NTSTATUS)0xe0000002)