diff --git a/lib/filters.js b/lib/filters.js
index 1c0e7916..733dab94 100644
--- a/lib/filters.js
+++ b/lib/filters.js
@@ -51,7 +51,7 @@ export const refFilter = (data, { domain, domainOnly, raw }) => {
   const links = {};
 
   const isValidRef = ref => {
-    return ref !== '' && !ref.startsWith('/') && !ref.startsWith('#');
+    return ref !== '' && ref !== null && !ref.startsWith('/') && !ref.startsWith('#');
   };
 
   if (raw) {