diff --git a/src/Xml/Dom/Manipulator/Document/optimize_namespaces.php b/src/Xml/Dom/Manipulator/Document/optimize_namespaces.php
index a1c1df7..1f351f2 100644
--- a/src/Xml/Dom/Manipulator/Document/optimize_namespaces.php
+++ b/src/Xml/Dom/Manipulator/Document/optimize_namespaces.php
@@ -9,6 +9,7 @@
 use function Psl\Vec\map;
 use function Psl\Vec\sort;
 use function Psl\Vec\values;
+use function VeeWee\Xml\Dom\Builder\xmlns_attribute;
 use function VeeWee\Xml\Dom\Locator\Xmlns\recursive_linked_namespaces;
 use function VeeWee\Xml\Dom\Manipulator\Xmlns\rename_element_namespace;
 
@@ -24,6 +25,8 @@ function optimize_namespaces(\DOM\XMLDocument $document, string $prefix = 'ns'):
     )));
 
     foreach (sort($namespaceURIs) as $index => $namespaceURI) {
+        $currentPrefix = $prefix . ((string) ($index+1));
+        xmlns_attribute($currentPrefix, $namespaceURI)($documentElement);
         rename_element_namespace($documentElement, $namespaceURI, $prefix . ((string) ($index+1)));
     }
 }
diff --git a/src/Xml/Dom/Manipulator/Xmlns/rename_element_namespace.php b/src/Xml/Dom/Manipulator/Xmlns/rename_element_namespace.php
index ab21156..0229941 100644
--- a/src/Xml/Dom/Manipulator/Xmlns/rename_element_namespace.php
+++ b/src/Xml/Dom/Manipulator/Xmlns/rename_element_namespace.php
@@ -5,42 +5,42 @@
 namespace VeeWee\Xml\Dom\Manipulator\Xmlns;
 
 use VeeWee\Xml\Exception\RuntimeException;
-use function VeeWee\Xml\Dom\Builder\xmlns_attribute;
-use function VeeWee\Xml\Dom\Predicate\is_element;
+use function VeeWee\Xml\Dom\Locator\Attribute\attributes_list;
+use function VeeWee\Xml\Dom\Locator\Element\children;
 use function VeeWee\Xml\Dom\Predicate\is_xmlns_attribute;
 
 /**
  * @throws RuntimeException
  * @param non-empty-string $newPrefix
  */
-function rename_element_namespace(\DOM\Element $root, string $namespaceURI, string $newPrefix): void
+function rename_element_namespace(\DOM\Element $element, string $namespaceURI, string $newPrefix): void
 {
+    children($element)->forEach(
+        static fn (\DOM\Element $child) => rename_element_namespace($child, $namespaceURI, $newPrefix)
+    );
 
-    $recurse = function (\DOM\Element $element) use (&$recurse, $namespaceURI, $newPrefix): void {
-        foreach ($element->childNodes as $child) {
-            if (is_element($child)) {
-                $recurse($child);
-            }
+    attributes_list($element)->forEach(static function (\DOM\Attr $attr) use ($namespaceURI, $newPrefix, $element) {
+        if ($attr->namespaceURI === $namespaceURI) {
+            $attr->rename($namespaceURI, $newPrefix . ':' . $attr->localName);
         }
 
-        $hasXmlnsAttribute = false;
-        foreach ($element->attributes as $attr) {
-            if ($attr->namespaceURI === $namespaceURI) {
-                $attr->rename($namespaceURI, $newPrefix . ':' . $attr->localName);
-            }
-
-            if (is_xmlns_attribute($attr) && $attr->value === $namespaceURI) {
+        if (is_xmlns_attribute($attr) && $attr->value === $namespaceURI) {
+            try {
                 $attr->rename($attr->namespaceURI, 'xmlns:' . $newPrefix);
-            }
-        }
 
-        if ($element->namespaceURI === $namespaceURI) {
-            $element->rename($namespaceURI, $newPrefix . ':' . $element->localName);
+            } catch (\DOMException $e) {
+                if ($e->getCode() === \DOM\INVALID_MODIFICATION_ERR) {
+                    // Remove the attribute that would become a duplicate
+                    $element->removeAttributeNode($attr);
+                } else {
+                    throw $e;
+                }
+            }
+            $attr->rename($attr->namespaceURI, 'xmlns:' . $newPrefix);
         }
-    };
+    });
 
-    $recurse(
-        // TODO - should become : xmlns_attribute($newPrefix, $namespaceURI)($root),
-        $root
-    );
+    if ($element->namespaceURI === $namespaceURI) {
+        $element->rename($namespaceURI, $newPrefix . ':' . $element->localName);
+    }
 }
diff --git a/tests/Xml/Dom/Configurator/OptimizeNamespacesTest.php b/tests/Xml/Dom/Configurator/OptimizeNamespacesTest.php
index f38d409..8f2224e 100644
--- a/tests/Xml/Dom/Configurator/OptimizeNamespacesTest.php
+++ b/tests/Xml/Dom/Configurator/OptimizeNamespacesTest.php
@@ -52,7 +52,7 @@ public function provideXmls()
             </schema>
             EOXML,
             <<<EOXML
-            <ns1:schema xmlns:ns1="http://www.w3.org/2001/XMLSchema" targetNamespace="http://soapinterop.org/store1">
+            <ns1:schema targetNamespace="http://soapinterop.org/store1" xmlns:ns1="http://www.w3.org/2001/XMLSchema">
                 <ns1:include schemaLocation="./store1.xsd"/>
             </ns1:schema>
             EOXML,
@@ -64,7 +64,7 @@ public function provideXmls()
             </schema>
             EOXML,
             <<<EOXML
-            <ns1:schema xmlns:ns1="http://www.w3.org/2001/XMLSchema" targetNamespace="http://soapinterop.org/store1">
+            <ns1:schema targetNamespace="http://soapinterop.org/store1" xmlns:ns1="http://www.w3.org/2001/XMLSchema">
                 <ns1:include schemaLocation="./store1.xsd"/>
             </ns1:schema>
             EOXML,
diff --git a/tests/Xml/Dom/Manipulator/Document/OptimizeNamespacesTest.php b/tests/Xml/Dom/Manipulator/Document/OptimizeNamespacesTest.php
index 01ffb87..a775cb7 100644
--- a/tests/Xml/Dom/Manipulator/Document/OptimizeNamespacesTest.php
+++ b/tests/Xml/Dom/Manipulator/Document/OptimizeNamespacesTest.php
@@ -106,7 +106,7 @@ public function provideXmls()
             </foo>
             EOXML,
             <<<EOXML
-            <foo xmlns:ns1="http://a" xmlns:ns2="http://z" version="1.9" target="universe">
+            <foo version="1.9" target="universe" xmlns:ns1="http://a" xmlns:ns2="http://z">
                 <item id="1" sku="jos">Jos</item>
                 <item sku="jaak" id="2">Jaak</item>
                 <item ns1:sku="jaak" ns2:id="3">Jul</item>