diff --git a/src/codegen.inc.php b/src/codegen.inc.php
index f40ba2a..4cba5b0 100644
--- a/src/codegen.inc.php
+++ b/src/codegen.inc.php
@@ -115,13 +115,16 @@ function apply_value_filters($field_name, array $tokens, $val, $add_assoc_check
 
     if(function_exists($filter_func))
     {
-      $args = array();
-      if($args_json)
+      $args = null;
+      if($args_json && (strpos($args_json, '[') === 0 || strpos($args_json, '{') === 0))
       {
         $args = json_decode($args_json, true);
         if(!is_array($args))
-          throw new Exception("Bad filter args: $args_json");
+          throw new Exception("Bad filter '$token' args: '$args_json'");
       }
+      else
+        $args = $args_json;
+
       if($add_assoc_check)
         $str = "(\$assoc ? $filter_func($str, '$field_name', \$this, " . str_replace("\n", "",  var_export($args, true)) . ") : $str)";
       else