diff --git a/plugins/OStatus/classes/Magicsig.php b/plugins/OStatus/classes/Magicsig.php
index 96900d8761..5a46aeeb6e 100644
--- a/plugins/OStatus/classes/Magicsig.php
+++ b/plugins/OStatus/classes/Magicsig.php
@@ -146,8 +146,10 @@ class Magicsig extends Memcached_DataObject
         
         $mod = base64_url_decode($matches[1]);
         $exp = base64_url_decode($matches[2]);
-        if ($matches[4]) {
+        if (!empty($matches[4])) {
             $private_exp = base64_url_decode($matches[4]);
+        } else {
+            $private_exp = false;
         }
 
         $params['public_key'] = new Crypt_RSA_KEY($mod, $exp, 'public');
diff --git a/plugins/OStatus/classes/Ostatus_profile.php b/plugins/OStatus/classes/Ostatus_profile.php
index 7b1aec76ba..93e8934c9e 100644
--- a/plugins/OStatus/classes/Ostatus_profile.php
+++ b/plugins/OStatus/classes/Ostatus_profile.php
@@ -1145,7 +1145,7 @@ class Ostatus_profile extends Memcached_DataObject
 
         if (!empty($poco)) {
             $url = $poco->getPrimaryURL();
-            if ($url->type == 'homepage') {
+            if ($url && $url->type == 'homepage') {
                 $homepage = $url->value;
             }
         }
diff --git a/plugins/OStatus/lib/discovery.php b/plugins/OStatus/lib/discovery.php
index 388df0a28f..f8449b309e 100644
--- a/plugins/OStatus/lib/discovery.php
+++ b/plugins/OStatus/lib/discovery.php
@@ -94,7 +94,7 @@ class Discovery
             $links = call_user_func(array($class, 'discover'), $uri);
             if ($link = Discovery::getService($links, Discovery::LRDD_REL)) {
                 // Load the LRDD XRD
-                if ($link['template']) {
+                if (!empty($link['template'])) {
                     $xrd_uri = Discovery::applyTemplate($link['template'], $uri);
                 } else {
                     $xrd_uri = $link['href'];
diff --git a/plugins/OStatus/lib/xrd.php b/plugins/OStatus/lib/xrd.php
index 16d27f8eb7..1de065db9f 100644
--- a/plugins/OStatus/lib/xrd.php
+++ b/plugins/OStatus/lib/xrd.php
@@ -53,17 +53,22 @@ class XRD
         $xrd = new XRD();
 
         $dom = new DOMDocument();
-        $dom->loadXML($xml);
+        if (!$dom->loadXML($xml)) {
+            throw new Exception("Invalid XML");
+        }
         $xrd_element = $dom->getElementsByTagName('XRD')->item(0);
 
         // Check for host-meta host
-        $host = $xrd_element->getElementsByTagName('Host')->item(0)->nodeValue;
+        $host = $xrd_element->getElementsByTagName('Host')->item(0);
         if ($host) {
-            $xrd->host = $host;
+            $xrd->host = $host->nodeValue;
         }
 
         // Loop through other elements
         foreach ($xrd_element->childNodes as $node) {
+            if (!($node instanceof DOMElement)) {
+                continue;
+            }
             switch ($node->tagName) {
             case 'Expires':
                 $xrd->expires = $node->nodeValue;