diff --git a/src/core/MString.js b/src/core/MString.js
index 137b561..19579d2 100644
--- a/src/core/MString.js
+++ b/src/core/MString.js
@@ -208,7 +208,7 @@ export default class MString {
     cIter += 3;
     for (; cIter < this.txt.length
       && !MString.isWhiteSpace(this.txt[cIter])
-      && (!enclosure  || this.txt[cIter] !== ')'); cIter += 1
+      && (!enclosure || this.txt[cIter] !== ')'); cIter += 1
     );
     if (cIter < this.iter + 4) {
       return null;
diff --git a/src/utils/ip.js b/src/utils/ip.js
index e0d0313..87f5f9b 100644
--- a/src/utils/ip.js
+++ b/src/utils/ip.js
@@ -119,6 +119,9 @@ export function getIPv6Subnet(ip) {
  * @return [start, end] with numerical IPs (32bit integer)
  */
 function ip4RangeStrToRangeNum(range) {
+  if (!range) {
+    return null;
+  }
   const [start, end] = range.split('-')
     .map(ip4ToNum);
   if (!start || !end || start > end) {
diff --git a/src/utils/whois.js b/src/utils/whois.js
index d3f30cb..9675401 100644
--- a/src/utils/whois.js
+++ b/src/utils/whois.js
@@ -18,13 +18,13 @@ function cIDRofWhois(ip, whoisData) {
     return whoisData.inet6num
       || (whoisData.range && !whoisData.range.includes('-') && whoisData.range)
       || whoisData.route
-      || 'N/A';
+      || null;
   }
   const { range } = whoisData;
-  if (range.includes('/') && !range.includes('-')) {
+  if (range && range.includes('/') && !range.includes('-')) {
     return range;
   }
-  return ip4InRangeToCIDR(ip, range) || 'N/A';
+  return ip4InRangeToCIDR(ip, range) || null;
 }
 
 /*
@@ -63,7 +63,7 @@ function parseWhois(ip, whoisData) {
   return {
     ip,
     country: countryFromWhois(whoisData),
-    cidr: cIDRofWhois(ip, whoisData),
+    cidr: cIDRofWhois(ip, whoisData) || 'N/A',
     org: orgFromWhois(whoisData),
     descr: whoisData.descr || 'N/A',
     asn: whoisData.asn || 'N/A',
@@ -71,7 +71,7 @@ function parseWhois(ip, whoisData) {
 }
 
 async function whois(ip) {
-  let whoisData = await whoiser.ip(ip);
+  const whoisData = await whoiser.ip(ip);
   if (whoisData.ReferralServer) {
     let referral = whoisData.ReferralServer;
     const prot = referral.indexOf('://');
@@ -79,9 +79,17 @@ async function whois(ip) {
       referral = referral.slice(prot + 3);
     }
     try {
-      whoisData = await whoiser.ip(ip, {
+      /*
+       * if referral whois server produces any error
+       * fallback to initial one
+       */
+      const refWhoisData = await whoiser.ip(ip, {
         host: referral,
       });
+      const refParsedData = parseWhois(ip, refWhoisData);
+      if (refParsedData.cidr !== 'N/A') {
+        return refParsedData;
+      }
     } catch {
       // nothing
     }