diff --git a/plinth/package.py b/plinth/package.py
index e4cfcf551..0550cfe7c 100644
--- a/plinth/package.py
+++ b/plinth/package.py
@@ -255,14 +255,26 @@ class Packages(app_module.FollowerComponent):
         Returns True if all of the packages are available in the user's Debian
         distribution or False otherwise. Returns True if it cannot be reliably
         determined whether the packages are available or not.
-        """
-        apt_lists_dir = pathlib.Path('/var/lib/apt/lists/')
-        num_files = len(
-            [child for child in apt_lists_dir.iterdir() if child.is_file()])
-        if num_files < 2:  # not counting the lock file
-            return True  # Don't know, package cache is not available
 
-        # List of all packages from all Package components
+        This operation can run for a long time as package cache may be
+        refreshed.
+        """
+        try:
+            self.get_actual_packages()
+            return True  # All packages were found in the cache
+        except MissingPackageError:
+            pass  # We will retry after refreshing package list
+
+        # If the package cache is new, then package is really not available.
+        package_cache = pathlib.Path('/var/cache/apt/pkgcache.bin')
+        if (package_cache.exists()
+                and time.time() - package_cache.stat().st_mtime < 3600):
+            return False
+
+        # Perform 'apt-get update'
+        refresh_package_lists()
+
+        # Check again for all the packages
         try:
             self.get_actual_packages()
         except MissingPackageError:
diff --git a/plinth/templates/setup.html b/plinth/templates/setup.html
index cbf6e316f..4523f7d7b 100644
--- a/plinth/templates/setup.html
+++ b/plinth/templates/setup.html
@@ -62,8 +62,7 @@
     <form class="form-install" action="" method="post">
       {% csrf_token %}
 
-      {% if has_unavailable_packages %}
-      {% elif package_conflicts and package_conflicts_action.value != 'ignore' %}
+      {% if package_conflicts and package_conflicts_action.value != 'ignore' %}
         <div class="alert alert-warning d-flex align-items-center" role="alert">
           <div class="me-2">
             <span class="fa fa-exclamation-triangle" aria-hidden="true"></span>
diff --git a/plinth/tests/test_package.py b/plinth/tests/test_package.py
index e553f644b..137418a97 100644
--- a/plinth/tests/test_package.py
+++ b/plinth/tests/test_package.py
@@ -3,6 +3,7 @@
 Test module for package module.
 """
 
+import time
 import unittest
 from unittest.mock import Mock, call, patch
 
@@ -338,23 +339,46 @@ def test_packages_find_conflicts(packages_installed_):
     assert component.find_conflicts() == ['package1', 'package2']
 
 
+@patch('plinth.package.refresh_package_lists')
 @patch('apt.Cache')
 @patch('pathlib.Path')
-def test_packages_is_available(path_class, cache):
+def test_packages_is_available(path_class, cache, refresh_package_lists):
     """Test checking for available packages."""
     path = Mock()
     path_class.return_value = path
-    path.iterdir.return_value = [Mock()]
 
+    # Packages found in cache
     component = Packages('test-component', ['package1', 'package2'])
-    assert component.is_available()
-
-    path.iterdir.return_value = [Mock(), Mock()]
     cache.return_value = ['package1', 'package2']
     assert component.is_available()
+    path_class.assert_not_called()
+    refresh_package_lists.assert_not_called()
 
+    # Packages not found, cache exists and is fresh
     cache.return_value = ['package1']
+    path.exists.return_value = True
+    path.stat.return_value.st_mtime = time.time()
     assert not component.is_available()
+    refresh_package_lists.assert_not_called()
+
+    # Packages not found, cache does not exist
+    cache.return_value = ['package1']
+    path.exists.return_value = False
+    assert not component.is_available()
+    refresh_package_lists.assert_called_once()
+
+    # Packages not found, cache is stale
+    cache.return_value = ['package1']
+    refresh_package_lists.reset_mock()
+    path.exists.return_value = True
+    path.stat.return_value.st_mtime = time.time() - 7200
+    assert not component.is_available()
+    refresh_package_lists.assert_called_once()
+
+    # Packages not found, cache is stale, but packages found after refresh
+    cache.side_effect = [['package1'], ['package1', 'package2']]
+    refresh_package_lists.reset_mock()
+    assert component.is_available()
 
 
 def test_packages_installed():
diff --git a/static/themes/default/js/main.js b/static/themes/default/js/main.js
index dbb4e8bd6..726a72714 100644
--- a/static/themes/default/js/main.js
+++ b/static/themes/default/js/main.js
@@ -210,7 +210,7 @@ function setSelectAllValue(parent) {
 /*
  * Check whether an app is available on its setup page.
  */
-document.addEventListener('DOMContentLoaded', function(event) {
+document.addEventListener('DOMContentLoaded', async () => {
     const checkingElement = document.querySelector('.app-checking-availability');
     if (!checkingElement)
         return;
@@ -225,11 +225,7 @@ document.addEventListener('DOMContentLoaded', function(event) {
 
     function setInstallButtonState(enable) {
         const installButton = document.querySelector('.install-button');
-        if (enable) {
-            installButton.removeAttribute('disabled');
-        } else {
-            installButton.setAttribute('disabled', 'disabled');
-        }
+        installButton?.setAttribute('disabled', !enable);
     }
 
     function unavailable() {
@@ -241,37 +237,30 @@ document.addEventListener('DOMContentLoaded', function(event) {
         const element = document.querySelector('.app-checking-availability-error');
         element.classList.remove('d-none');
         checkingElement.classList.add('d-none');
-        setInstallButtonState(true);  // Allow trying installation
+        setInstallButtonState(true); // Allow trying installation
     }
 
-    let request = new XMLHttpRequest();
-    request.timeout = 2 * 60 * 1000;  // 2 minutes
-    request.onload = function() {
-        // Remove the progress spinner
+    try {
+        setInstallButtonState(false);
+        const response = await fetch(`/plinth/is-available/${appId}/`, {
+            timeout: 2 * 60 * 1000  // 2 minutes
+        });
+
         checkingElement.classList.add('d-none');
 
-        let available = false;
-        if (this.status === 200) {
-            try {
-                const response = JSON.parse(this.responseText);
-                if (response.is_available === true) {
-                    setInstallButtonState(true);
-                } else if (response.is_available === false) {
-                    unavailable();
-                } else {
-                    error();
-                }
-            } catch (e) {
+        if (response.ok) {
+            const data = await response.json();
+            if (data.is_available === true) {
+                setInstallButtonState(true);
+            } else if (data.is_available === false) {
+                unavailable();
+            } else {
                 error();
             }
         } else {
             error();
         }
-    };
-    request.onerror = error;
-    request.ontimeout = error;
-
-    request.open('GET', `/plinth/is-available/${appId}/`, true);
-    setInstallButtonState(false);
-    request.send();
+    } catch {
+        error();
+    }
 });