diff --git a/internal/dnsforward/http.go b/internal/dnsforward/http.go
index 76f88edc..5d4738de 100644
--- a/internal/dnsforward/http.go
+++ b/internal/dnsforward/http.go
@@ -340,7 +340,13 @@ func (req *jsonDNSConfig) checkPrivateRDNS(
 	sysResolvers SystemResolvers,
 	privateNets netutil.SubnetSet,
 ) (err error) {
-	if (req.UsePrivateRDNS == nil || !*req.UsePrivateRDNS) && req.LocalPTRUpstreams == nil {
+	switch {
+	case
+		req.UsePrivateRDNS != nil && *req.UsePrivateRDNS,
+		req.LocalPTRUpstreams != nil && len(*req.LocalPTRUpstreams) > 0:
+		// Only check the private RDNS servers if its usage has just been
+		// enabled or if it contains any addresses.
+	default:
 		return nil
 	}