205.1b

Some effects change an object’s card type, supertype, or subtype but specify that the object retains a prior card type, supertype, or subtype. In such cases, all the object’s prior card types, supertypes, and subtypes are retained. This rule applies to effects that use phrases such as “in addition to its other types” or that state that something is “still a [type, supertype, or subtype].” Some effects state that an object becomes an “artifact creature”; these effects also allow the object to retain all of its prior card types and subtypes. Some effects state that an object becomes a “[creature type or types] artifact creature”; these effects also allow the object to retain all of its prior card types and subtypes other than creature types, but replace any existing creature types.