Vocab, hashes and lexemes

Why does this code throw an error?

from spacy.lang.en import English
from spacy.lang.de import German

# Create an English and German nlp object
nlp = English()
nlp_de = German()

# Get the ID for the string 'Bowie'
bowie_id = nlp.vocab.strings['Bowie']
print(bowie_id)

# Look up the ID for 'Bowie' in the vocab
print(nlp_de.vocab.strings[bowie_id])

The English language class is already available as the nlp object.