diff --git a/roles/netbootxyz/templates/menu/boot.cfg.j2 b/roles/netbootxyz/templates/menu/boot.cfg.j2
index be8b0f2cfc..d4c5844d80 100644
--- a/roles/netbootxyz/templates/menu/boot.cfg.j2
+++ b/roles/netbootxyz/templates/menu/boot.cfg.j2
@@ -2,22 +2,22 @@
 
 :global_vars
 # set site name
-set site_name {{ site_name }}
+isset ${site_name} || set site_name {{ site_name }}
 
 # set boot domain
-set boot_domain {{ boot_domain }}
+isset ${boot_domain} || set boot_domain {{ boot_domain }}
 
 # set location of memdisk
-set memdisk {{ memdisk_location }}
+isset ${memdisk} || set memdisk {{ memdisk_location }}
 
 # set location of custom netboot.xyz live assets, override in local-vars.ipxe
 isset ${live_endpoint} || set live_endpoint {{ live_endpoint }}
 
 # signature check enabled?
-set sigs_enabled {{ sigs_enabled | default(false) | bool | lower }}
+isset ${sigs_enabled} || set sigs_enabled {{ sigs_enabled | default(false) | bool | lower }}
 
 # set location of signatures for sources
-set sigs {{ sigs_location }}
+isset ${sigs} || set sigs {{ sigs_location }}
 
 # set location of latest iPXE
 iseq ${platform} efi && set ipxe_disk netboot.xyz-snponly.efi || set ipxe_disk netboot.xyz-undionly.kpxe
@@ -32,8 +32,8 @@ isset ${boot_timeout} || set boot_timeout {{ boot_timeout }}
 {% for key, value in releases.items() | sort(attribute='1.name') %}
 {% if value.mirror is defined and value.base_dir is defined %}
 ### {{ value.name }}
-set {{ key }}_mirror {{ value.mirror }}
-set {{ key }}_base_dir {{ value.base_dir }}
+isset {{ '${' + key + '_mirror}' }} || set {{ key }}_mirror {{ value.mirror }}
+isset {{ '${' + key + '_base_dir}' }} || set {{ key }}_base_dir {{ value.base_dir }}
 
 {% endif %}
 {% endfor %}
@@ -100,7 +100,7 @@ iseq ${ipxe_cloud_config} packet && goto metal ||
 goto clouds_end
 
 :gce
-set cmdline console=ttyS0,115200n8
+isset ${cmdline} || set cmdline console=ttyS0,115200n8
 goto clouds_end
 
 :metal
@@ -110,7 +110,7 @@ iseq ${arch} arm64 && goto metal_arm64 ||
 goto clouds_end
 
 :metal_x86_64
-set cmdline console=ttyS1,115200n8
+isset ${cmdline} || set cmdline console=ttyS1,115200n8
 iseq ${platform} efi && set ipxe_disk netboot.xyz-metal-snp.efi || set ipxe_disk netboot.xyz-metal.kpxe
 set menu_linux_i386 0
 set menu_freedos 0
@@ -119,7 +119,7 @@ iseq ${platform} efi && set menu_pci 0 ||
 goto clouds_end
 
 :metal_arm64
-set cmdline console=ttyAMA0,115200
+isset ${cmdline} || set cmdline console=ttyAMA0,115200
 set ipxe_disk netboot.xyz-metal-arm64-snp.efi
 set menu_bsd 1
 set menu_freedos 0
diff --git a/roles/netbootxyz/templates/menu/debian.ipxe.j2 b/roles/netbootxyz/templates/menu/debian.ipxe.j2
index f3bc025ef1..305eb3c9b5 100644
--- a/roles/netbootxyz/templates/menu/debian.ipxe.j2
+++ b/roles/netbootxyz/templates/menu/debian.ipxe.j2
@@ -38,7 +38,7 @@ set dir ${debian_base_dir}/dists/${debian_version}/main/installer-${os_arch}/cur
 goto deb_boot_type
 
 :mirrorcfg
-set debian_mirror ${debian_mirror}
+# debian_mirror is set in boot.cfg.j2 with isset guard, no need to reassign
 set mirrorcfg mirror/suite=${debian_version}
 set dir ${debian_base_dir}/dists/${debian_version}/main/installer-${os_arch}/current/images/netboot/
 goto deb_boot_type