diff --git a/helpers/SynapseHelper.php b/helpers/SynapseHelper.php
index 670aad1..7a14dd0 100644
--- a/helpers/SynapseHelper.php
+++ b/helpers/SynapseHelper.php
@@ -35,7 +35,10 @@ class SynapseHelper {
             return null;
         }
 
-        $matrixId = '@' . rawurlencode($username) . ':' . $domain;
+        // Build the Matrix user ID and percent-encode it once for the URL path.
+        // rawurlencode($username) here would double-encode any special chars when
+        // the full $matrixId string is encoded again below.
+        $matrixId = '@' . $username . ':' . $domain;
         $url      = rtrim($baseUrl, '/') . '/_synapse/admin/v2/users/' . rawurlencode($matrixId);
 
         $ch = curl_init($url);