diff --git a/xCAT-test/unit/debian_arch_map.t b/xCAT-test/unit/debian_arch_map.t
index 08c140cec..a98df8224 100644
--- a/xCAT-test/unit/debian_arch_map.t
+++ b/xCAT-test/unit/debian_arch_map.t
@@ -16,6 +16,11 @@ use xCAT::Utils;
 # --- what debootstrap and the package lists are given ----------------------
 is(xCAT::Utils->debian_arch('x86_64'), 'amd64',
     'Debian calls x86_64 amd64');
+# genimage passes this value to debootstrap --arch and reads it to pick the apt mirror, and
+# debootstrap knows i386, not xCAT's x86.
+is(xCAT::Utils->debian_arch('x86'), 'i386',
+    'debian_arch: the 32-bit x86 token becomes i386');
+
 is(xCAT::Utils->debian_arch('ppc64el'), 'ppc64el',
     'the Debian name for POWER LE is unchanged');
 is(xCAT::Utils->debian_arch('ppc64le'), 'ppc64le',
diff --git a/xCAT-test/unit/ubuntu_genimage_apt_mirror.t b/xCAT-test/unit/ubuntu_genimage_apt_mirror.t
index 172ab8b47..c3ad36a43 100644
--- a/xCAT-test/unit/ubuntu_genimage_apt_mirror.t
+++ b/xCAT-test/unit/ubuntu_genimage_apt_mirror.t
@@ -14,6 +14,8 @@ use Test::More;
 # evaluated here, so this test tracks the script rather than a copy of it.
 
 my $repo_root = File::Spec->rel2abs( File::Spec->catdir( $FindBin::Bin, '..', '..' ) );
+use lib "$FindBin::Bin/../../perl-xCAT";
+require xCAT::Utils;
 my $genimage_path = File::Spec->catfile(
     $repo_root, 'xCAT-server', 'share', 'xcat', 'netboot', 'ubuntu', 'genimage'
 );
@@ -29,6 +31,14 @@ my ($pick) = $src =~ /^\s*(my \$mirror = \(defined \$aptmirror\[0\].*?;)\s*$/ms;
 ok( defined $pick, 'found the mirror override in genimage' )
   or done_testing(), exit;
 
+# genimage does not read osimage.osarch directly: it converts it first, so the value the selection
+# sees is whatever xCAT::Utils::debian_arch returns. Driving the xCAT token through that conversion
+# is what catches a token the map does not know.
+sub choose_osarch {
+    my ( $osarch, $site ) = @_;
+    return choose( xCAT::Utils->debian_arch($osarch), $site );
+}
+
 sub choose {
     my ( $uarch, $site ) = @_;
     my $set = defined $site ? "('$site')" : "()";
@@ -57,4 +67,14 @@ is( choose( 'amd64', 'http://mirror.example.invalid/ubuntu' ),
 is( choose( 'riscv64', '' ), 'http://ports.ubuntu.com/ubuntu-ports',
     'an empty site.ubuntu_apt_mirror does not blank the mirror' );
 
+# The architecture reaches the selection as an xCAT osarch value, not as a Debian one.
+is( choose_osarch('x86_64'), 'http://archive.ubuntu.com/ubuntu',
+    'osarch x86_64 reaches the archive' );
+is( choose_osarch('x86'), 'http://archive.ubuntu.com/ubuntu',
+    'osarch x86 reaches the archive, which is where i386 lives' );
+is( choose_osarch('riscv64'), 'http://ports.ubuntu.com/ubuntu-ports',
+    'osarch riscv64 reaches the ports archive' );
+is( choose_osarch('ppc64el'), 'http://ports.ubuntu.com/ubuntu-ports',
+    'osarch ppc64el reaches the ports archive' );
+
 done_testing();