diff --git a/library/Icinga/File/Pdf.php b/library/Icinga/File/Pdf.php
index 242e2ddd8..912109b02 100644
--- a/library/Icinga/File/Pdf.php
+++ b/library/Icinga/File/Pdf.php
@@ -8,6 +8,7 @@ use Dompdf\Dompdf;
 use Dompdf\Options;
 use Icinga\Application\Icinga;
 use Icinga\Exception\ProgrammingError;
+use Icinga\Util\Format;
 use Icinga\Web\Hook;
 use Icinga\Web\Url;
 
@@ -45,8 +46,17 @@ class Pdf
     public function renderControllerAction($controller)
     {
         $this->assertNoHeadersSent();
-        ini_set('memory_limit', '384M');
-        ini_set('max_execution_time', 300);
+
+        $memLimit = 512 * 1024 ** 2;
+        if (Format::unpackShorthandBytes(ini_get('memory_limit')) < $memLimit) {
+            ini_set('memory_limit', $memLimit);
+        }
+
+        $maxExecTime = 300;
+        if ((int) ini_get('max_execution_time') < $maxExecTime) {
+            ini_set('max_execution_time', $maxExecTime);
+        }
+
         $viewRenderer = $controller->getHelper('viewRenderer');
         $controller->render(
             $viewRenderer->getScriptAction(),
diff --git a/library/Icinga/Util/Format.php b/library/Icinga/Util/Format.php
index b43be49cc..f3e682128 100644
--- a/library/Icinga/Util/Format.php
+++ b/library/Icinga/Util/Format.php
@@ -4,8 +4,6 @@
 namespace Icinga\Util;
 
 use DateTime;
-use Icinga\Date\DateFormatter;
-use Icinga\Exception\ProgrammingError;
 
 class Format
 {
@@ -141,4 +139,37 @@ class Format
 
         return $dt->format('L') == 1;
     }
+
+    /**
+     * Unpack shorthand bytes PHP directives to bytes
+     *
+     * @param   string  $subject
+     *
+     * @return  int
+     */
+    public static function unpackShorthandBytes($subject)
+    {
+        $base = (int) $subject;
+
+        if ($base <= -1) {
+            return INF;
+        }
+
+        switch (strtoupper($subject[strlen($subject) - 1])) {
+            case 'K':
+                $multiplier = 1024;
+                break;
+            case 'M':
+                $multiplier = 1024 ** 2;
+                break;
+            case 'G':
+                $multiplier = 1024 ** 3;
+                break;
+            default:
+                $multiplier = 1;
+                break;
+        }
+
+        return $base * $multiplier;
+    }
 }