It is not kosher to have #ifdefs inside macros.

bin/varnishd/mgt/mgt_main.c

@@ -395,6 +395,10 @@ init_params(struct cli *cli)
 		MCF_SetDefault("gzip_buffer", "4k");
 	}
 
+#if !defined(HAVE_ACCEPT_FILTERS) || defined(__linux)
+	MCF_SetDefault("accept_filter", "off");
+#endif
+
 	low = sysconf(_SC_THREAD_STACK_MIN);
 	bprintf(stackmin, "%jd", (intmax_t)low);
 	MCF_SetMinimum("thread_pool_stack", stackmin);

include/tbl/params.h

@@ -35,11 +35,7 @@ PARAM(
 	/* typ */	bool,
 	/* min */	NULL,
 	/* max */	NULL,
-#if defined(HAVE_ACCEPT_FILTERS) || defined(__linux)
 	/* default */	"on",
-#else
-	/* default */	"off",
-#endif /* HAVE_ACCEPT_FILTERS || __linux */
 	/* units */	"bool",
 	/* flags */	MUST_RESTART,
 	/* s-text */