Inja can't render json objects due to wrong quotation marks

[hwiedPro]

Given the following template:

{ "some_key": {{ A_JSON_OBJECT_VARIABLE }} }

The variable A_JSON_OBJECT_VARIABLE is defined as follows:

nl::json variables = nl::json{
  {"A_JSON_OBJECT_VARIABLE",
    {
      {"key1", "value1"}, {"key2", "value2"}
    }
  }
}

When now rendering with inja this is the result:

{ "some_key": "{"key1":"value1","key2":"value2"}" }

However we expected something like this:

{ "some_key": {"key1":"value1","key2":"value2"} }

PS: Indexing the inner keys works