diff --git a/src/Encoder/OptionalElementEncoder.php b/src/Encoder/OptionalElementEncoder.php
index fb77a14..ad18d8d 100644
--- a/src/Encoder/OptionalElementEncoder.php
+++ b/src/Encoder/OptionalElementEncoder.php
@@ -51,6 +51,8 @@ public function iso(Context $context): IsoInterface
             return $elementIso;
         }
 
+        $xsiNamespace = Xmlns::xsi()->value();
+
         return new Iso(
             /**
              * @param T|null $raw
@@ -63,7 +65,7 @@ public function iso(Context $context): IsoInterface
             /**
              * @return T|null
              */
-            static function (ElementList|Element|string $xml) use ($elementIso, $isList) : mixed {
+            static function (ElementList|Element|string $xml) use ($elementIso, $isList, $xsiNamespace) : mixed {
                 if ($xml === '') {
                     return null;
                 }
@@ -79,7 +81,7 @@ static function (ElementList|Element|string $xml) use ($elementIso, $isList) : m
                     $parsedXml instanceof Element => $parsedXml->element(),
                     default => null
                 };
-                if ($documentElement && $documentElement->getAttributeNS(Xmlns::xsi()->value(), 'nil') === 'true') {
+                if ($documentElement && $documentElement->getAttributeNS($xsiNamespace, 'nil') === 'true') {
                     return null;
                 }
 
diff --git a/src/Xml/Reader/ElementValueReader.php b/src/Xml/Reader/ElementValueReader.php
index e5865c3..48c2210 100644
--- a/src/Xml/Reader/ElementValueReader.php
+++ b/src/Xml/Reader/ElementValueReader.php
@@ -7,8 +7,6 @@
 use Soap\Encoding\Encoder\Context;
 use Soap\Encoding\Encoder\XmlEncoder;
 use VeeWee\Reflecta\Iso\IsoInterface;
-use function Psl\Type\string;
-use function VeeWee\Xml\Dom\Locator\Node\value as readValue;
 
 final class ElementValueReader
 {
@@ -30,9 +28,7 @@ public function __invoke(
      */
     public static function forEncoder(Context $context, XmlEncoder $encoder, Element $element): mixed
     {
-        return $encoder->iso($context)->from(
-            readValue($element, string())
-        );
+        return $encoder->iso($context)->from($element->substitutedNodeValue);
     }
 
     /**
@@ -41,8 +37,6 @@ public static function forEncoder(Context $context, XmlEncoder $encoder, Element
      */
     public static function forIso(IsoInterface $iso, Element $element): mixed
     {
-        return $iso->from(
-            readValue($element, string())
-        );
+        return $iso->from($element->substitutedNodeValue);
     }
 }