diff --git a/system/init.php b/system/init.php
index 41cfb053..25d12427 100644
--- a/system/init.php
+++ b/system/init.php
@@ -131,6 +131,10 @@ if($cache->enabled() && $cache->fetch('vocations', $tmp)) {
 	$config['vocations'] = unserialize($tmp);
 }
 else {
+	if(!class_exists('DOMDocument')) {
+		throw new RuntimeException('Please install PHP xml extension. MyAAC will not work without it.');
+	}
+
 	$vocations = new DOMDocument();
 	$file = $config['data_path'] . 'XML/vocations.xml';
 	if(!@file_exists($file))
diff --git a/system/libs/plugins.php b/system/libs/plugins.php
index 700f451c..c757cd98 100644
--- a/system/libs/plugins.php
+++ b/system/libs/plugins.php
@@ -93,6 +93,10 @@ class Plugins {
 	public static function install($file) {
 		global $db;
 
+		if(!\class_exists('ZipArchive')) {
+			throw new RuntimeException('Please install PHP zip extension. Plugins upload disabled until then.');
+		}
+
 		$zip = new ZipArchive();
 		if($zip->open($file)) {
 			for ($i = 0; $i < $zip->numFiles; $i++) {
diff --git a/system/libs/pot/OTS.php b/system/libs/pot/OTS.php
index 0a0a6c7f..d20d029c 100644
--- a/system/libs/pot/OTS.php
+++ b/system/libs/pot/OTS.php
@@ -366,9 +366,8 @@ class POT
     public function connect($params)
     {
         // checks if PDO extension is loaded
-        if( !extension_loaded('PDO') )
-        {
-            throw new LogicException();
+        if( !extension_loaded('PDO') ) {
+            throw new RuntimeException('Please install PHP pdo extension. MyAAC will not work without it.');
         }
 
         $this->db = new OTS_DB_MySQL($params);