diff --git a/lib/www/client/source/src/main.js b/lib/www/client/source/src/main.js
index ab80b5d..fc4527c 100644
--- a/lib/www/client/source/src/main.js
+++ b/lib/www/client/source/src/main.js
@@ -16,8 +16,8 @@ Vue.filter('markdown', markdown);
 Vue.filter('markdownInline', markdownInline);
 Vue.filter('position', (str, item, opts) => 
   str
-  .replace(/@POS(ITION)?@/g, geometryAsString(item, opts))
-  .replace(/@DMS@/g, geometryAsString(item, {...opts, dms:true}))
+  .replace(/@POS(ITION)?@/g, geometryAsString(item, opts) || "(position unknown)")
+  .replace(/@DMS@/g, geometryAsString(item, {...opts, dms:true}) || "(position unknown)")
 );
 // Vue.filter('position', (str, item, opts) => str.replace(/@POS(ITION)?@/, "☺"));