diff --git a/usr.sbin/bsdinstall/scripts/zfsboot b/usr.sbin/bsdinstall/scripts/zfsboot
--- a/usr.sbin/bsdinstall/scripts/zfsboot
+++ b/usr.sbin/bsdinstall/scripts/zfsboot
@@ -71,7 +71,7 @@
 #
 # Should we use sysctl(8) vfs.zfs.min_auto_ashift=12 to force 4K sectors?
 #
-: ${ZFSBOOT_FORCE_4K_SECTORS:=1}
+: ${ZFSBOOT_FORCE_4K_SECTORS=1}
 
 #
 # Should we use geli(8) to encrypt the drives?