diff --git a/src/codegen.inc.php b/src/codegen.inc.php
index b87c96f..f2d1998 100644
--- a/src/codegen.inc.php
+++ b/src/codegen.inc.php
@@ -113,7 +113,9 @@ function apply_filters($token_prefix, $field_name, array $tokens, $val, $add_ass
     if(function_exists($filter_func))
     {
       $args = null;
-      if($args_json && (strpos($args_json, '[') === 0 || strpos($args_json, '{') === 0))
+      if($args_json && 
+        ((strpos($args_json, '[') === 0 && strlen($args_json) > 1 && $args_json[strlen($args_json)-1] === ']') || 
+         (strpos($args_json, '{') === 0 && strlen($args_json) > 1 && $args_json[strlen($args_json)-1] === '}')))
       {
         $args = json_decode($args_json, true);
         if(!is_array($args))