1 files changed, 1 insertions, 1 deletions

diff --git a/src/dumbymap.mjs b/src/dumbymap.mjs
index 4d1a2ed..fb89d61 100644
--- a/src/dumbymap.mjs
+++ b/src/dumbymap.mjs
@@ -165,7 +165,7 @@ export const generateMaps = (container, {
   /** LINK: Add external symbol on anchors */
   container.querySelectorAll('a')
     .forEach(a => {
-      if (a.href.startsWith('http') && !a.href.startsWith(window.location.origin)) {
+      if (typeof a.href === 'string' && a.href.startsWith('http') && !a.href.startsWith(window.location.origin)) {
         a.classList.add('external')
       }
     })