In an embodiment, a class definition of a class may provide an indication whether a property, which is part of the class, is immutable. The indication may be made implicitly or explicitly. A value of the property may be established (e.g., set) during a creation of an instance of the class. An attempt to set the value of the property after the instance is created may be disallowed. Further, an error (e.g., an error message, exception condition) may be reported in response to disallowing the attempt.