DuH!

We already had a check that took care of this in an architecture
independent way.

bin/varnishtest/tests/c00005.vtc

@@ -9,6 +9,18 @@ server s1 {
 	txresp -body "2222\n"
 } -start
 
+varnish v1 -errvcl {foo} {
+	sub vcl_recv {
+		if (client.ip ~ acl1) {
+			set req.url = "/";
+		}
+	}
+
+	backend acl1 {
+		.host = "127.0.0.1";
+	}
+}
+
 varnish v1 -arg "-p vsl_mask=+VCL_trace" -vcl+backend {
 	sub vcl_recv {
 		if (client.ip ~ acl1) {

include/tbl/params.h

@@ -1505,7 +1505,7 @@ PARAM(
 	/* name */	vsl_space,
 	/* typ */	bytes,
 	/* min */	"1M",
-	/* max */	"4294967295",	// 4G-1
+	/* max */	NULL,
 	/* default */	"80M",
 	/* units */	"bytes",
 	/* flags */	MUST_RESTART,