diff --git a/setup/start.sh b/setup/start.sh
index 9b2ca292..824ff859 100755
--- a/setup/start.sh
+++ b/setup/start.sh
@@ -86,7 +86,7 @@ if [ -z "$PRIMARY_HOSTNAME" ]; then
 
 		# Take the part after the @-sign as the user's domain name, and add
 		# 'box.' to the beginning to create a default hostname for this machine.
-		DEFAULT_PRIMARY_HOSTNAME=box.$(echo $EMAIL_ADDR | sed 's/.*@//')
+		DEFAULT_PRIMARY_HOSTNAME=box.$(echo $EMAIL_ADDR | sed -e 's/.*@//' -e 's/^box\.//')
 	fi
 
 	echo