diff --git a/libc/kernel/uapi/linux/gtp.h b/libc/kernel/uapi/linux/gtp.h
index 20bc3d6..ff55116 100644
--- a/libc/kernel/uapi/linux/gtp.h
+++ b/libc/kernel/uapi/linux/gtp.h
@@ -45,5 +45,5 @@
   GTPA_PAD,
   __GTPA_MAX,
 };
-#define GTPA_MAX (__GTPA_MAX + 1)
+#define GTPA_MAX (__GTPA_MAX - 1)
 #endif