diff --git a/lib/prepare-params.js b/lib/prepare-params.js
index 1b63786..b53027c 100644
--- a/lib/prepare-params.js
+++ b/lib/prepare-params.js
@@ -44,7 +44,7 @@ export function prepareParams(item, {reverse, columns, citycode, postcode, lat,
 
   if (!reverse && columns) {
     const stringToGeocode = columns
-      .map(c => c in item ? item[c].trim() : '')
+      .map(c => typeof item[c] === 'string' ? item[c].trim() : '')
       .join(' ')
       .trim()