diff --git a/phpseclib/File/X509.php b/phpseclib/File/X509.php
index 304b8386..dac4cfca 100644
--- a/phpseclib/File/X509.php
+++ b/phpseclib/File/X509.php
@@ -670,7 +670,8 @@ class X509
      */
     private function mapOutExtensions(&$root, $path)
     {
-        foreach ($this->extensionValues as $id => [$critical, $value]) {
+        foreach ($this->extensionValues as $id => $value) {
+            list($critical, $value) = $value;
             $root['tbsCertificate']['extensions'][] = [
                 'extnId' => $id,
                 'extnValue' => $value,