diff --git a/src/node/handler/PadMessageHandler.js b/src/node/handler/PadMessageHandler.js
index eb3a784a2..8621a750c 100644
--- a/src/node/handler/PadMessageHandler.js
+++ b/src/node/handler/PadMessageHandler.js
@@ -1496,8 +1496,12 @@ exports.padUsers = async function(padID) {
     let s = sessioninfos[roomClient.id];
     if (s) {
       return authorManager.getAuthor(s.author).then(author => {
-        author.id = s.author;
-        padUsers.push(author);
+        // Fixes: https://github.com/ether/etherpad-lite/issues/4120
+        // On restart author might not be populated?
+        if(author){
+          author.id = s.author;
+          padUsers.push(author);
+        }
       });
     }
   }));