diff --git a/sys/contrib/openzfs/include/os/freebsd/zfs/sys/zfs_context_os.h b/sys/contrib/openzfs/include/os/freebsd/zfs/sys/zfs_context_os.h
index 1ce72330412c..457fa3af8142 100644
--- a/sys/contrib/openzfs/include/os/freebsd/zfs/sys/zfs_context_os.h
+++ b/sys/contrib/openzfs/include/os/freebsd/zfs/sys/zfs_context_os.h
@@ -78,7 +78,7 @@ extern int hz;
 extern int tick;
 typedef int fstrans_cookie_t;
 #define	spl_fstrans_mark() (0)
-#define	spl_fstrans_unmark(x) (x = 0)
+#define	spl_fstrans_unmark(x) ((void)x)
 #define	signal_pending(x) SIGPENDING(x)
 #define	current curthread
 #define	thread_join(x)