diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index 4feda2d..548240d 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -23,7 +23,7 @@
 };
 #define uc_uid			uc_base.cr_uid
 
-#define UNX_WRITESLACK		(21 + (UNX_MAXNODENAME >> 2))
+#define UNX_WRITESLACK		(21 + XDR_QUADLEN(UNX_MAXNODENAME))
 
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 # define RPCDBG_FACILITY	RPCDBG_AUTH