This is what I have in my setup:
set system login user aebooth authentication public-keys aebooth@w520 key AAAAB3NzaC1yc2EAAAABIwAAAQEA35pkgSDkGD9so98XXDfGJo/bP5ZpFgz/hQlSgcS6kLosci//mg/cp7Yy/cqFphXuu38U7hTxaHeaQHqk+Efio6T+7fuuWNP1Azcb2xuJjzarrRqwpwYAdD13V2rkH0t3HT1kOtKqVA1e9+D1RnDuozT+4Yk86MCuqZ2m8T3GylyTb6kIjBHid/s57ExOhmNzxVCxf9XQdseHlygidzl2xPV8KxgW6AT/QqOYcWkaYfzp/1WU7qB/um+IHB/du9DUAz7IdSYsbKyq7LeLozTCvBHSG+yWerm0J7IxoVAdTAA4KILEZ8goJAJpWNGqoMeDUC1YqPorh4pEauhvr9cC+w==
set system login user aebooth authentication public-keys aebooth@w520 type ssh-rsa
I think the space is getting you in trouble. Not sure if you meant this as a bug report or a question looking for a workaround.