diff --git a/.github/scripts/tests/test_installer_apt_refresh.py b/.github/scripts/tests/test_installer_apt_refresh.py
new file mode 100644
index 00000000..34a5fa89
--- /dev/null
+++ b/.github/scripts/tests/test_installer_apt_refresh.py
@@ -0,0 +1,69 @@
+"""A Proxmox host without a subscription is refused by the enterprise
+repositories on every apt refresh. The installers tell that apart from a
+refresh that really failed."""
+from pathlib import Path
+import re
+import subprocess
+import tempfile
+from unittest import TestCase
+
+ROOT = Path(__file__).resolve().parents[3]
+INSTALLERS = ('install_proxmenux.sh', 'install_proxmenux_beta.sh')
+
+ENTERPRISE = """Hit:1 http://deb.debian.org/debian trixie InRelease
+Err:2 https://enterprise.proxmox.com/debian/ceph-squid trixie InRelease
+  401  Unauthorized [IP: 51.91.38.34 443]
+Err:4 https://enterprise.proxmox.com/debian/pve trixie InRelease
+  401  Unauthorized [IP: 51.91.38.34 443]
+Reading package lists...
+E: Failed to fetch https://enterprise.proxmox.com/debian/ceph-squid/dists/trixie/InRelease  401  Unauthorized [IP: 51.91.38.34 443]
+E: The repository 'https://enterprise.proxmox.com/debian/ceph-squid trixie InRelease' is not signed.
+E: Failed to fetch https://enterprise.proxmox.com/debian/pve/dists/trixie/InRelease  401  Unauthorized [IP: 51.91.38.34 443]
+E: The repository 'https://enterprise.proxmox.com/debian/pve trixie InRelease' is not signed.
+"""
+NETWORK = """Err:1 http://deb.debian.org/debian trixie InRelease
+  Temporary failure resolving 'deb.debian.org'
+E: Failed to fetch http://deb.debian.org/debian/dists/trixie/InRelease  Temporary failure resolving 'deb.debian.org'
+"""
+LOCKED = "E: Could not get lock /var/lib/apt/lists/lock. It is held by process 4321 (apt-get)\n"
+# apt reports a repository it cannot reach as a warning, not as an error.
+UNREACHABLE = """Err:6 http://repo.invalid/debian trixie InRelease
+  Could not resolve 'repo.invalid'
+W: Failed to fetch http://repo.invalid/debian/dists/trixie/InRelease  Could not resolve 'repo.invalid'
+W: Some index files failed to download. They have been ignored, or old ones used instead.
+"""
+
+
+def function(installer, name):
+    source = (ROOT / installer).read_text()
+    return re.search(rf'^{name}\(\) \{{\n.*?^\}}\n', source, re.MULTILINE | re.DOTALL)[0]
+
+
+class InstallerAptRefresh(TestCase):
+    def refused(self, installer, log):
+        with tempfile.NamedTemporaryFile('w', suffix='.log') as handle:
+            handle.write(log)
+            handle.flush()
+            script = function(installer, 'apt_only_enterprise_refused') + \
+                f'APT_ERROR_LOG={handle.name if log is not None else ""}\napt_only_enterprise_refused\n'
+            return subprocess.run(['bash', '-c', script], capture_output=True).returncode == 0
+
+    def test_a_refresh_refused_only_by_the_enterprise_repositories_is_good(self):
+        for installer in INSTALLERS:
+            self.assertTrue(self.refused(installer, ENTERPRISE), installer)
+
+    def test_any_other_failure_is_still_a_failure(self):
+        for installer in INSTALLERS:
+            self.assertFalse(self.refused(installer, NETWORK), installer)
+            self.assertFalse(self.refused(installer, LOCKED), installer)
+            self.assertFalse(self.refused(installer, ENTERPRISE + NETWORK), installer)
+            self.assertFalse(self.refused(installer, ENTERPRISE + UNREACHABLE), installer)
+            self.assertFalse(self.refused(installer, 'Reading package lists...\n'), installer)
+
+    def test_the_refresh_step_asks_before_it_warns(self):
+        for installer in INSTALLERS:
+            source = (ROOT / installer).read_text()
+            step = source[source.index('if run_apt update -y; then'):]
+            step = step[:step.index('\n    fi\n')]
+            self.assertLess(step.index('elif apt_only_enterprise_refused; then'), step.index('apt cache refresh failed'))
+            self.assertIn('discard_apt_error', step[step.index('elif'):step.index('else\n')])
diff --git a/install_proxmenux.sh b/install_proxmenux.sh
index 10d12cbe..d387c0e5 100755
--- a/install_proxmenux.sh
+++ b/install_proxmenux.sh
@@ -360,6 +360,15 @@ discard_apt_error() {
     APT_ERROR_LOG=""
 }
 
+# A Proxmox host without a subscription is refused by the enterprise
+# repositories. Every other repository is refreshed, so that refresh is good.
+apt_only_enterprise_refused() {
+    [ -n "$APT_ERROR_LOG" ] && [ -f "$APT_ERROR_LOG" ] || return 1
+    local failures
+    failures=$(grep -E '^(E: |Err:|W: Failed to fetch)' "$APT_ERROR_LOG") || return 1
+    ! grep -qv 'enterprise\.proxmox\.com' <<<"$failures"
+}
+
 show_progress() {
     local step="$1"
     local total="$2"
@@ -707,6 +716,9 @@ install_normal_version() {
     msg_info "Refreshing apt cache..."
     if run_apt update -y; then
         msg_ok "apt cache refreshed."
+    elif apt_only_enterprise_refused; then
+        discard_apt_error
+        msg_ok "apt cache refreshed. The Proxmox enterprise repositories need a subscription and were skipped."
     else
         msg_warn "apt cache refresh failed; checking available packages."
         show_apt_error
diff --git a/install_proxmenux_beta.sh b/install_proxmenux_beta.sh
index b1388b7b..f4a42059 100644
--- a/install_proxmenux_beta.sh
+++ b/install_proxmenux_beta.sh
@@ -164,6 +164,15 @@ discard_apt_error() {
     APT_ERROR_LOG=""
 }
 
+# A Proxmox host without a subscription is refused by the enterprise
+# repositories. Every other repository is refreshed, so that refresh is good.
+apt_only_enterprise_refused() {
+    [ -n "$APT_ERROR_LOG" ] && [ -f "$APT_ERROR_LOG" ] || return 1
+    local failures
+    failures=$(grep -E '^(E: |Err:|W: Failed to fetch)' "$APT_ERROR_LOG") || return 1
+    ! grep -qv 'enterprise\.proxmox\.com' <<<"$failures"
+}
+
 show_progress() {
     echo -e "\n${BOLD}${BL}${TAB}Installing ProxMenux Beta: Step ${1} of ${2}${CL}"
     echo
@@ -638,6 +647,9 @@ install_beta() {
     msg_info "Refreshing apt cache..."
     if run_apt update -y; then
         msg_ok "apt cache refreshed."
+    elif apt_only_enterprise_refused; then
+        discard_apt_error
+        msg_ok "apt cache refreshed. The Proxmox enterprise repositories need a subscription and were skipped."
     else
         msg_warn "apt cache refresh failed; checking available packages."
         show_apt_error