diff --git a/lib/SimpleSAML/XML/Signer.php b/lib/SimpleSAML/XML/Signer.php
index f84a335448fa88d654228595e444827841d55b68..e4a04e05ae4bcf4db0998e5bdb95f6e9235475d9 100644
--- a/lib/SimpleSAML/XML/Signer.php
+++ b/lib/SimpleSAML/XML/Signer.php
@@ -20,28 +20,26 @@ use SimpleSAML\Utils\Config;
 
 class Signer
 {
-
-
     /**
      * @var string The name of the ID attribute.
      */
-    private $idAttrName;
+    private $idAttrName = '';
 
     /**
      * @var XMLSecurityKey|bool  The private key (as an XMLSecurityKey).
      */
-    private $privateKey;
+    private $privateKey = false;
 
     /**
-     * @var string The certificate (as text).
+     * @var string|bool The certificate (as text).
      */
-    private $certificate;
+    private $certificate = false;
 
 
     /**
      * @var array Extra certificates which should be included in the response.
      */
-    private $extraCertificates;
+    private $extraCertificates = array();
 
 
     /**
@@ -64,11 +62,6 @@ class Signer
     {
         assert(is_array($options));
 
-        $this->idAttrName = false;
-        $this->privateKey = false;
-        $this->certificate = false;
-        $this->extraCertificates = array();
-
         if (array_key_exists('privatekey', $options)) {
             $pass = null;
             if (array_key_exists('privatekey_pass', $options)) {
@@ -291,7 +284,7 @@ class Signer
         $objXMLSecDSig->setCanonicalMethod(XMLSecurityDSig::EXC_C14N);
 
         $options = array();
-        if ($this->idAttrName !== false) {
+        if (!empty($this->idAttrName)) {
             $options['id_name'] = $this->idAttrName;
         }