diff --git a/settings.php b/settings.php
index 793a30d4..09fabfe4 100644
--- a/settings.php
+++ b/settings.php
@@ -291,7 +291,7 @@
     $name = 'format_topcoll/defaulttoggleiconsize';
     $title = get_string('defaulttoggleiconsize', 'format_topcoll');
     $description = get_string('defaulttoggleiconsize_desc', 'format_topcoll');
-    $default = 'medium';
+    $default = 'tc-medium';
     $choices = array(
         'tc-small' => new lang_string('small', 'format_topcoll'),
         'tc-medium' => new lang_string('medium', 'format_topcoll'),
@@ -498,4 +498,4 @@
         '4.0' => new lang_string('em4_0', 'format_topcoll')
     );
     $settings->add(new admin_setting_configselect($name, $title, $description, $default, $choices));
-}
\ No newline at end of file
+}