diff --git a/inc/instance-config.php b/inc/instance-config.php
index 3e359f65..22c2d03a 100644
--- a/inc/instance-config.php
+++ b/inc/instance-config.php
@@ -209,6 +209,7 @@ $config['allowed_ext_files'][] = 'pdf';
 $config['allowed_ext_files'][] = 'txt';
 $config['allowed_ext_files'][] = 'epub';
 $config['allowed_ext_files'][] = 'djvu';
+$config['allowed_ext_files'][] = 'opus';
 // Compressed files
 $config['allowed_ext_files'][] = 'zip';
 $config['allowed_ext_files'][] = 'gz';