diff --git a/i.php b/i.php
index 1cf683aed..652b095dc 100644
--- a/i.php
+++ b/i.php
@@ -365,6 +365,15 @@ function send_derivative($expires)
   fclose($fp);
 }
 
+function safe_unserialize($value)
+{
+  if (is_string($value))
+  {
+    return unserialize($value);
+  }
+  return $value;
+}
+
 $page=array();
 $begin = $step = microtime(true);
 $timing=array();
@@ -388,7 +397,17 @@ catch (Exception $e)
 }
 pwg_db_check_charset();
 
-list($conf['derivatives']) = pwg_db_fetch_row(pwg_query('SELECT value FROM '.$prefixeTable.'config WHERE param=\'derivatives\''));
+$query = '
+SELECT param, value
+  FROM '.$prefixeTable.'config
+  WHERE param IN (\'derivatives\', \'disabled_derivatives\')
+;';
+
+$result = pwg_query($query);
+while ($row = pwg_db_fetch_assoc($result))
+{
+  $conf[ $row['param'] ] = $row['value'];
+}
 ImageStdParams::load_from_db();
 
 
diff --git a/include/derivative_std_params.inc.php b/include/derivative_std_params.inc.php
index 64bac673a..48a96351d 100644
--- a/include/derivative_std_params.inc.php
+++ b/include/derivative_std_params.inc.php
@@ -103,11 +103,13 @@ final class ImageStdParams
    */
   static function get_disabled_type_map()
   {
+    global $conf;
+
     if (count(self::$disabled_type_map))
     {
       return self::$disabled_type_map;
     }
-    return conf_get_param('disabled_derivatives', array());
+    return $conf['disabled_derivatives'] ?? array();
   }
 
   /**
@@ -178,9 +180,16 @@ final class ImageStdParams
     {
       self::$watermark = new WatermarkParams();
       self::$type_map = self::get_enabled_default_sizes();
-      self::$disabled_type_map = self::get_disabled_default_sizes();
-      self::save();
+      self::save(false);
     }
+
+    self::$disabled_type_map = safe_unserialize(self::get_disabled_type_map());
+    if (empty(self::$disabled_type_map))
+    {
+      self::$disabled_type_map = self::get_disabled_default_sizes();
+      self::save_disabled();
+    }
+    
     self::build_maps();
   }
 
@@ -200,14 +209,14 @@ final class ImageStdParams
   static function set_and_save($map)
   {
     self::$type_map = $map;
-    self::save();
+    self::save(false);
     self::build_maps();
   }
 
   /**
    * Saves the configuration in database.
    */
-  static function save()
+  static function save($save_disabled = true)
   {
     $ser = serialize( array(
       'd' => self::$type_map,
@@ -217,7 +226,10 @@ final class ImageStdParams
       ) );
     conf_update_param('derivatives', addslashes($ser) );
 
-    self::save_disabled();
+    if ($save_disabled)
+    {
+      self::save_disabled();
+    }
   }
 
   /**