Rule 208.3a

If an effect would be created that sets the base power and/or toughness of a noncreature permanent, or otherwise modifies its power and/or toughness, that effect is created even though it doesn’t do anything unless that permanent becomes a creature. Example: Veteran Motorist has the ability “Whenever Veteran Motorist crews a Vehicle, that Vehicle gets +1/+1 until end of turn,” and it’s tapped to pay the crew cost of a Vehicle. This triggered ability resolves while the Vehicle it crewed isn’t yet a creature. The continuous effect is created and will apply to the Vehicle once it becomes a creature.

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