diff --git a/admin/cli/install.php b/admin/cli/install.php
index 4b373820943..b37161c6ad4 100644
--- a/admin/cli/install.php
+++ b/admin/cli/install.php
@@ -636,6 +636,23 @@ if (!file_exists($configfile)) {
     cli_error('Can not create config file.');
 }
 
+// Test environment first.
+list($envstatus, $environment_results) = check_moodle_environment(normalize_version($release), ENV_SELECT_RELEASE);
+if (!$envstatus) {
+    $errors = environment_get_errors($environment_results);
+    cli_heading(get_string('environment', 'admin'));
+    foreach ($errors as $error) {
+        list($info, $report) = $error;
+        echo "!! $info !!\n$report\n\n";
+    }
+    exit(1);
+}
+
+// Test plugin dependancies.
+if (!plugin_manager::instance()->all_plugins_ok($version)) {
+    cli_error(get_string('pluginschecktodo', 'admin'));
+}
+
 // remember selected language
 $installlang = $CFG->lang;
 // return back to original dir before executing setup.php which changes the dir again
diff --git a/admin/cli/upgrade.php b/admin/cli/upgrade.php
index 6f49cc1a1a9..31a23c27805 100644
--- a/admin/cli/upgrade.php
+++ b/admin/cli/upgrade.php
@@ -93,7 +93,7 @@ if ($version < $CFG->version) {
 $oldversion = "$CFG->release ($CFG->version)";
 $newversion = "$release ($version)";
 
-// test environment first
+// Test environment first.
 list($envstatus, $environment_results) = check_moodle_environment(normalize_version($release), ENV_SELECT_RELEASE);
 if (!$envstatus) {
     $errors = environment_get_errors($environment_results);
@@ -105,6 +105,11 @@ if (!$envstatus) {
     exit(1);
 }
 
+// Test plugin dependancies.
+if (!plugin_manager::instance()->all_plugins_ok($version)) {
+    cli_error(get_string('pluginschecktodo', 'admin'));
+}
+
 if ($interactive) {
     $a = new stdClass();
     $a->oldversion = $oldversion;
diff --git a/admin/index.php b/admin/index.php
index 631f7890162..10220d24e41 100644
--- a/admin/index.php
+++ b/admin/index.php
@@ -212,8 +212,8 @@ if ($version > $CFG->version) {  // upgrade
         $PAGE->set_cacheable(false);
 
         $output = $PAGE->get_renderer('core', 'admin');
-        echo $this->upgrade_environment_page($release, $envstatus, $environment_results);
-        die;
+        echo $output->upgrade_environment_page($release, $envstatus, $environment_results);
+        die();
 
     } else if (empty($confirmplugins)) {
         $strplugincheck = get_string('plugincheck');
@@ -224,7 +224,7 @@ if ($version > $CFG->version) {  // upgrade
         $PAGE->set_cacheable(false);
 
         $output = $PAGE->get_renderer('core', 'admin');
-        echo $output->upgrade_plugin_check_page(plugin_manager::instance(), $showallplugins,
+        echo $output->upgrade_plugin_check_page(plugin_manager::instance(), $version, $showallplugins,
                 new moodle_url('/admin/index.php', array('confirmupgrade' => 1, 'confirmrelease' => 1)),
                 new moodle_url('/admin/index.php', array('confirmupgrade'=>1, 'confirmrelease'=>1, 'confirmplugincheck'=>1)));
         die();
@@ -257,7 +257,7 @@ if (moodle_needs_upgrading()) {
             $PAGE->set_cacheable(false);
 
             $output = $PAGE->get_renderer('core', 'admin');
-            echo $output->upgrade_plugin_check_page(plugin_manager::instance(), $showallplugins,
+            echo $output->upgrade_plugin_check_page(plugin_manager::instance(), $version, $showallplugins,
                     new moodle_url('/admin/index.php'),
                     new moodle_url('/admin/index.php', array('confirmplugincheck'=>1)));
             die();
diff --git a/admin/renderer.php b/admin/renderer.php
index c90c4130ce0..e74c0951ac8 100644
--- a/admin/renderer.php
+++ b/admin/renderer.php
@@ -119,7 +119,7 @@ class core_admin_renderer extends plugin_renderer_base {
             $output .= $this->upgrade_reload(new moodle_url('/admin/index.php'), array('confirmupgrade' => 1));
 
         } else {
-            echo $output->notification(get_string('environmentok', 'admin'), 'notifysuccess');
+            $output .= $this->notification(get_string('environmentok', 'admin'), 'notifysuccess');
 
             if (empty($CFG->skiplangupgrade) and current_language() !== 'en') {
                 $output .= $this->box(get_string('langpackwillbeupdated', 'admin'), 'generalbox', 'notice');
@@ -137,19 +137,23 @@ class core_admin_renderer extends plugin_renderer_base {
      * Display the upgrade page that lists all the plugins that require attention.
      * @return string HTML to output.
      */
-    public function upgrade_plugin_check_page($pluginman, $showallplugins, $reloadurl, $continueurl) {
+    public function upgrade_plugin_check_page($pluginman, $version, $showallplugins, $reloadurl, $continueurl) {
         $output = '';
 
         $output .= $this->header();
         $output .= $this->box_start('generalbox');
         $output .= $this->container(get_string('pluginchecknotice', 'core_plugin'), 'generalbox', 'notice');
-        $output .= $this->plugins_check_table($pluginman, array('full' => $showallplugins));
+        $output .= $this->plugins_check_table($pluginman, $version, array('full' => $showallplugins));
         $output .= $this->box_end();
         $output .= $this->upgrade_reload($reloadurl);
 
-        $button = new single_button($continueurl, get_string('upgradestart', 'admin'), 'get');
-        $button->class = 'continuebutton';
-        $output .= $this->render($button);
+        if ($pluginman->all_plugins_ok($version)) {
+            $button = new single_button($continueurl, get_string('upgradestart', 'admin'), 'get');
+            $button->class = 'continuebutton';
+            $output .= $this->render($button);
+        } else {
+            $output .= $this->box(get_string('pluginschecktodo', 'admin'), 'environmentbox errorbox');
+        }
 
         $output .= $this->footer();
 
@@ -388,11 +392,11 @@ class core_admin_renderer extends plugin_renderer_base {
      *     (bool)full = false: whether to display up-to-date plugins, too
      *
      * @param plugin_manager $pluginman provides information about the plugins.
+     * @param int $version the version of the Moodle code from version.php.
      * @param array $options rendering options
      * @return string HTML code
      */
-    public function plugins_check_table(plugin_manager $pluginman, array $options = null) {
-        global $CFG;
+    public function plugins_check_table(plugin_manager $pluginman, $version, array $options = null) {
         $plugininfo = $pluginman->get_plugins();
 
         if (empty($plugininfo)) {
@@ -475,7 +479,7 @@ class core_admin_renderer extends plugin_renderer_base {
 
                 $status = new html_table_cell(get_string('status_' . $statuscode, 'core_plugin'));
 
-                $requires = new html_table_cell($this->required_column($plugin, $pluginman));
+                $requires = new html_table_cell($this->required_column($plugin, $pluginman, $version));
 
                 $statusisboring = in_array($statuscode, array(
                         plugin_manager::PLUGIN_STATUS_NODB, plugin_manager::PLUGIN_STATUS_UPTODATE));
@@ -537,12 +541,11 @@ class core_admin_renderer extends plugin_renderer_base {
      * @param plugin_information $plugin the plugin we are rendering the row for.
      * @param plugin_manager $pluginman provides data on all the plugins.
      */
-    protected function required_column($plugin, $pluginman) {
-        global $CFG;
+    protected function required_column($plugin, $pluginman, $version) {
         $requires = array();
 
         if (!empty($plugin->versionrequires)) {
-            if ($plugin->versionrequires <= $CFG->version) {
+            if ($plugin->versionrequires <= $version) {
                 $class = 'requires-ok';
             } else {
                 $class = 'requires-failed';
diff --git a/lang/en/admin.php b/lang/en/admin.php
index 0f626f871c6..19d1da0cd4e 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -745,6 +745,7 @@ $string['pleaserefreshregistration'] = 'Your site has been registered with moodl
 $string['pleaseregister'] = 'Please register your site to remove this button';
 $string['plugin'] = 'Plugin';
 $string['plugins'] = 'Plugins';
+$string['pluginschecktodo'] = 'You must solve all the plugin requirements before proceeding to install this Moodle version!';
 $string['pluginsoverview'] = 'Plugins overview';
 $string['profilecategory'] = 'Category';
 $string['profilecategoryname'] = 'Category name (must be unique)';
diff --git a/lib/pluginlib.php b/lib/pluginlib.php
index cbbc062f419..6f2c8bb0d99 100644
--- a/lib/pluginlib.php
+++ b/lib/pluginlib.php
@@ -235,8 +235,6 @@ class plugin_manager {
      * @return bool true if all the dependancies are satisfied.
      */
     public function are_dependancies_satisfied($dependancies) {
-        $installedplugins = $this->get_plugins();
-
         foreach ($dependancies as $component => $requiredversion) {
             $otherplugin = $this->get_plugin_info($component);
             if (is_null($otherplugin)) {
@@ -251,6 +249,28 @@ class plugin_manager {
         return true;
     }
 
+    /**
+     * Checks all dependancies for all installed plugins. Used by install and upgrade.
+     * @param int $moodleversion the version from version.php.
+     * @return bool true if all the dependancies are satisfied for all plugins.
+     */
+    public function all_plugins_ok($moodleversion) {
+        foreach ($this->get_plugins() as $type => $plugins) {
+            foreach ($plugins as $plugin) {
+
+                if (!empty($plugin->versionrequires) && $plugin->versionrequires > $moodleversion) {
+                    return false;
+                }
+
+                if (!$this->are_dependancies_satisfied($plugin->get_other_required_plugins())) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
     /**
      * Defines a white list of all plugins shipped in the standard Moodle distribution
      *