diff --git a/src/codegen.inc.php b/src/codegen.inc.php
index 0bef3e9..3bbbdaf 100644
--- a/src/codegen.inc.php
+++ b/src/codegen.inc.php
@@ -329,7 +329,11 @@ function add_twig_filters(\Twig\Environment $twig)
     'json_tag',
     function(\mtgMetaField $field): string {
       $tag = get_field_alias_or_name($field);
-      return $tag.',string';
+      $type = $field->getType();
+      if($type instanceof \mtgBuiltinType && !$type->isString() && !$type->isBlob()) {
+        return $tag.',string';
+      }
+      return $tag;
     }
   ));
 }