diff --git a/lib/activity.php b/lib/activity.php
index 85d3efa21a..8d7ae1540b 100644
--- a/lib/activity.php
+++ b/lib/activity.php
@@ -440,7 +440,7 @@ class Activity
         }
 
         foreach ($this->categories as $cat) {
-            $xs->raw($cat->asString());
+            $cat->outputTo($xs);
         }
 
         // can be either URLs or enclosure objects
diff --git a/lib/activityobject.php b/lib/activityobject.php
index 3df35f84b0..b5e6013b4b 100644
--- a/lib/activityobject.php
+++ b/lib/activityobject.php
@@ -570,7 +570,7 @@ class ActivityObject
         }
 
         if (!empty($this->poco)) {
-            $xo->raw($this->poco->asString());
+            $this->poco->outputTo($xo);
         }
 
         foreach ($this->extra as $el) {
diff --git a/lib/atomcategory.php b/lib/atomcategory.php
index 9763023f75..e527877cb0 100644
--- a/lib/atomcategory.php
+++ b/lib/atomcategory.php
@@ -59,6 +59,13 @@ class AtomCategory
     }
 
     function asString()
+    {
+        $xs = new XMLStringer();
+        $this->outputTo($xs);
+        return $xs->getString();
+    }
+
+    function outputTo($xo)
     {
         $attribs = array();
         if ($this->term !== null) {
@@ -70,8 +77,6 @@ class AtomCategory
         if ($this->label !== null) {
             $attribs['label'] = $this->label;
         }
-        $xs = new XMLStringer();
-        $xs->element('category', $attribs);
-        return $xs->getString();
+        $xo->element('category', $attribs);
     }
 }
diff --git a/lib/poco.php b/lib/poco.php
index 2157062b37..d7b082163e 100644
--- a/lib/poco.php
+++ b/lib/poco.php
@@ -211,30 +211,34 @@ class PoCo
     function asString()
     {
         $xs = new XMLStringer(true);
-        $xs->element(
+        $this->outputTo($xs);
+        return $xs->getString();
+    }
+
+    function outputTo($xo)
+    {
+        $xo->element(
             'poco:preferredUsername',
             null,
             $this->preferredUsername
         );
 
-        $xs->element(
+        $xo->element(
             'poco:displayName',
             null,
             $this->displayName
         );
 
         if (!empty($this->note)) {
-            $xs->element('poco:note', null, common_xml_safe_str($this->note));
+            $xo->element('poco:note', null, common_xml_safe_str($this->note));
         }
 
         if (!empty($this->address)) {
-            $xs->raw($this->address->asString());
+            $this->address->outputTo($xo);
         }
 
         foreach ($this->urls as $url) {
-            $xs->raw($url->asString());
+            $url->outputTo($xo);
         }
-
-        return $xs->getString();
     }
 }
diff --git a/lib/pocoaddress.php b/lib/pocoaddress.php
index 60873bdc42..d9f6ff2bde 100644
--- a/lib/pocoaddress.php
+++ b/lib/pocoaddress.php
@@ -43,14 +43,17 @@ class PoCoAddress
 
     function asString()
     {
-        if (!empty($this->formatted)) {
-            $xs = new XMLStringer(true);
-            $xs->elementStart('poco:address');
-            $xs->element('poco:formatted', null, common_xml_safe_str($this->formatted));
-            $xs->elementEnd('poco:address');
-            return $xs->getString();
-        }
+        $xs = new XMLStringer(true);
+        $this->outputTo($xs);
+        return $xs->getString();
+    }
 
-        return null;
+    function outputTo($xo)
+    {
+        if (!empty($this->formatted)) {
+            $xo->elementStart('poco:address');
+            $xo->element('poco:formatted', null, common_xml_safe_str($this->formatted));
+            $xo->elementEnd('poco:address');
+        }
     }
 }
diff --git a/lib/pocourl.php b/lib/pocourl.php
index 803484d760..786793b280 100644
--- a/lib/pocourl.php
+++ b/lib/pocourl.php
@@ -53,13 +53,18 @@ class PoCoURL
     function asString()
     {
         $xs = new XMLStringer(true);
-        $xs->elementStart('poco:urls');
-        $xs->element('poco:type', null, $this->type);
-        $xs->element('poco:value', null, $this->value);
-        if (!empty($this->primary)) {
-            $xs->element('poco:primary', null, 'true');
-        }
-        $xs->elementEnd('poco:urls');
+        $this->outputTo($xs);
         return $xs->getString();
     }
+
+    function outputTo($xo)
+    {
+        $xo->elementStart('poco:urls');
+        $xo->element('poco:type', null, $this->type);
+        $xo->element('poco:value', null, $this->value);
+        if (!empty($this->primary)) {
+            $xo->element('poco:primary', null, 'true');
+        }
+        $xo->elementEnd('poco:urls');
+    }
 }