diff --git a/src/lib/publicsuffixlist/publicsuffixlist.js b/src/lib/publicsuffixlist/publicsuffixlist.js
index 0a01278e0..73cc367cd 100644
--- a/src/lib/publicsuffixlist/publicsuffixlist.js
+++ b/src/lib/publicsuffixlist/publicsuffixlist.js
@@ -331,6 +331,7 @@ const setHostnameArg = function(hostname) {
     const buf = pslBuffer8;
     if ( hostname === hostnameArg ) { return buf[LABEL_INDICES_SLOT]; }
     if ( hostname === null || hostname.length === 0 ) {
+        hostnameArg = '';
         return (buf[LABEL_INDICES_SLOT] = 0);
     }
     hostname = hostname.toLowerCase();