diff --git a/src/plugins/utils.js b/src/plugins/utils.js
index 652ae68..1122cb8 100644
--- a/src/plugins/utils.js
+++ b/src/plugins/utils.js
@@ -389,8 +389,12 @@ class Util {
     }
 
     /** Generate a random user name */
-    randomUser() {
-        return "weblite-" + this.randomString(
+    randomUser(prefix) {
+        var pfx = prefix ? prefix.replace(/[^0-9a-zA-Z\-_]/gi, '') : null;
+        if (!pfx || pfx.length == 0) {
+            pfx = "weblite-";
+        }
+        return pfx + this.randomString(
             12,
             "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
         );
diff --git a/src/services/matrix.service.js b/src/services/matrix.service.js
index 1265a0c..ce0ac87 100644
--- a/src/services/matrix.service.js
+++ b/src/services/matrix.service.js
@@ -115,7 +115,7 @@ export default {
             // can not use avatars and 3. They can not seamlessly be upgraded to real accounts.
             //
             // Instead, we use an ILAG approach, Improved Landing as Guest.
-            const user = util.randomUser();
+            const user = util.randomUser(this.$config.userIdPrefix);
             const pass = util.randomPass();
             promiseLogin = tempMatrixClient
               .register(user, pass, null, {
@@ -854,7 +854,7 @@ export default {
             if (tempUser) {
               clientPromise = Promise.resolve(tempUser);
             } else {
-              const user = util.randomUser();
+              const user = util.randomUser(this.$config.userIdPrefix);
               const pass = util.randomPass();
               clientPromise = tempMatrixClient
                 .register(user, pass, null, {