diff --git a/libc/kernel/tools/cpp.py b/libc/kernel/tools/cpp.py
index 8b2b709..c0b379b 100755
--- a/libc/kernel/tools/cpp.py
+++ b/libc/kernel/tools/cpp.py
@@ -2587,10 +2587,12 @@
         text = """\
 #define SIGRTMIN 32
 #define SIGRTMAX _NSIG
+#define SIGRTMAX(a,class) some_func(a, class)
 """
         expected = """\
 #define __SIGRTMIN 32
 #define __SIGRTMAX _KERNEL__NSIG
+#define __SIGRTMAX(a,__linux_class) some_func(a, __linux_class)
 """
         self.assertEqual(self.parse(text), expected)