diff --git a/lib/influx.js b/lib/influx.js
index 759b17b..c96e5bc 100644
--- a/lib/influx.js
+++ b/lib/influx.js
@@ -7,6 +7,8 @@ const internal = require('./internal');
 const debug = require('./debug');
 const util = require('./util');
 
+const influxInt = new RegExp('^[0-9]+i$');
+
 function convert(v) {
   if (!_.isString(v)) {
     return v;
@@ -25,7 +27,7 @@ function isBoolean(v) {
 
 function formatFields(data) {
   return _.map(data, (v, k) => {
-    if (_.isString(v) && v.charAt(v.length - 1) !== 'i' && !isBoolean(v)) {
+    if (_.isString(v) && !influxInt.test(v) && !isBoolean(v)) {
       return `${convert(k)}="${v}"`;
     }
     return `${convert(k)}=${convert(v)}`;