As described under the captain, players must store their unloaded goods at the end of the captain phase. When players do not have sufficient storage space, they must return the goods to the goods supplies.
Owners of an occupied small warehouse may store, at the end of the captain phase, in addition to the single good they are allowed to store on their windrose, all the goods of one kind that they choose. The warehouse protects the player from returning goods to the supply. It does not protect the player from being required to load the goods onto the cargo ships.
Note: The goods chosen are not actually stored on the small warehouse tile, but on the player’s windrose.