diff --git a/src/parsers.js b/src/parsers.js
index 016a7f1..c809e12 100644
--- a/src/parsers.js
+++ b/src/parsers.js
@@ -96,7 +96,7 @@ const parseSimpleWhois = (whois) => {
 			} else if (isGroup) {
 				data[isGroup] = group
 			} else {
-				for (key in group) {
+				for (const key in group) {
 					const label = renameLabels[key] || key
 					data[label] = group[key]
 				}