diff --git a/files/constants.php b/files/constants.php
index 598e0817..35211860 100644
--- a/files/constants.php
+++ b/files/constants.php
@@ -108,6 +108,7 @@
 // Core types entities
 const PHPFHIR_TYPES_INTERFACE_TYPE = 'TypeInterface';
 const PHPFHIR_TYPES_INTERFACE_DSTU1_TYPE = 'DSTU1TypeInterface';
+const PHPFHIR_TYPES_INTERFACE_DSTU1_PRIMITIVE_CONTAINER_TYPE = 'DSTU1PrimitiveContainerTypeInterface';
 const PHPFHIR_TYPES_INTERFACE_PRIMITIVE_TYPE = 'PrimitiveTypeInterface';
 const PHPFHIR_TYPES_INTERFACE_ELEMENT_TYPE = 'ElementTypeInterface';
 const PHPFHIR_TYPES_INTERFACE_PRIMITIVE_CONTAINER_TYPE = 'PrimitiveContainerTypeInterface';
diff --git a/src/Utilities/ImportUtils.php b/src/Utilities/ImportUtils.php
index a4aeb09a..4098967e 100644
--- a/src/Utilities/ImportUtils.php
+++ b/src/Utilities/ImportUtils.php
@@ -69,6 +69,8 @@ public static function buildVersionTypeImports(Version $version, Type $type): vo
 
         $logger->debug(sprintf('Compiling imports for Type "%s"...', $type->getFHIRName()));
 
+        $sourceMeta = $version->getSourceMetadata();
+
         $imports = $type->getImports();
 
         // immediately add self
@@ -110,7 +112,7 @@ public static function buildVersionTypeImports(Version $version, Type $type): vo
             $imports->addCoreFileImportsByName(
                 PHPFHIR_TYPES_INTERFACE_RESOURCE_TYPE,
             );
-        } else {
+        } else if (!$sourceMeta->isDSTU1()) {
             $imports->addCoreFileImportsByName(
                 PHPFHIR_TYPES_INTERFACE_ELEMENT_TYPE,
             );
@@ -128,6 +130,10 @@ public static function buildVersionTypeImports(Version $version, Type $type): vo
             $imports->addCoreFileImportsByName(PHPFHIR_CLASSNAME_CONSTANTS);
         }
 
+        if ($sourceMeta->isDSTU1()) {
+            $imports->addCoreFileImportsByName(PHPFHIR_TYPES_INTERFACE_RESOURCE_TYPE);
+        }
+
         if ($typeKind->isResourceContainer($type->getVersion())) {
             $imports->addVersionCoreFileImportsByName(
                 $type->getVersion(),
@@ -181,7 +187,7 @@ public static function buildVersionTypeImports(Version $version, Type $type): vo
                 $imports->addVersionCoreFileImportsByName($type->getVersion(), PHPFHIR_VERSION_CLASSNAME_VERSION_TYPE_MAP);
                 $imports->addVersionCoreFileImportsByName($type->getVersion(), PHPFHIR_VERSION_CLASSNAME_VERSION);
             } else {
-                $valProp = match(true) {
+                $valProp = match (true) {
                     $propertyType->isPrimitiveContainer() => $propertyType->getProperties()->getProperty(PHPFHIR_VALUE_PROPERTY_NAME),
                     $propertyType->hasPrimitiveContainerParent() => $propertyType->getParentProperty(PHPFHIR_VALUE_PROPERTY_NAME),
                     default => null,
diff --git a/src/Utilities/NameUtils.php b/src/Utilities/NameUtils.php
index e671c08e..29073692 100644
--- a/src/Utilities/NameUtils.php
+++ b/src/Utilities/NameUtils.php
@@ -118,6 +118,7 @@ class NameUtils
         'xml' => 'XML',
         'http' => 'HTTP',
         'curl' => 'CURL',
+        'dstu1' => 'DSTU1',
     ];
 
     /** @var array */
diff --git a/src/Version/Definition/Type.php b/src/Version/Definition/Type.php
index 77fab403..3d2e53ba 100644
--- a/src/Version/Definition/Type.php
+++ b/src/Version/Definition/Type.php
@@ -848,6 +848,16 @@ public function getDirectlyImplementedInterfaces(): array
         $interfaces = [];
         $coreFiles = $this->_version->getConfig()->getCoreFiles();
         $versionCoreFiles = $this->_version->getCoreFiles();
+        $sourceMeta = $this->_version->getSourceMetadata();
+
+        // dstu1 has its own special type interface
+        if ($sourceMeta->isDSTU1() && !$this->isPrimitiveOrListType() && !$this->hasPrimitiveOrListParent()) {
+            if (null === $this->getParentType()) {
+                $interfaces[PHPFHIR_TYPES_INTERFACE_DSTU1_TYPE] = $coreFiles
+                    ->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_DSTU1_TYPE)
+                    ->getFullyQualifiedNamespace(false);
+            }
+        }
 
         // first, determine which base type interface it must implement
         if ($this->isPrimitiveOrListType()) {
@@ -858,9 +868,15 @@ public function getDirectlyImplementedInterfaces(): array
             }
         } else if ($this->isPrimitiveContainer()) {
             if (!$this->hasPrimitiveContainerParent()) {
-                $interfaces[PHPFHIR_TYPES_INTERFACE_PRIMITIVE_CONTAINER_TYPE] = $coreFiles
-                    ->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_PRIMITIVE_CONTAINER_TYPE)
-                    ->getFullyQualifiedNamespace(false);
+                if ($sourceMeta->isDSTU1()) {
+                    $interfaces[PHPFHIR_TYPES_INTERFACE_DSTU1_PRIMITIVE_CONTAINER_TYPE] = $coreFiles
+                        ->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_PRIMITIVE_CONTAINER_TYPE)
+                        ->getFullyQualifiedNamespace(false);
+                } else {
+                    $interfaces[PHPFHIR_TYPES_INTERFACE_PRIMITIVE_CONTAINER_TYPE] = $coreFiles
+                        ->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_PRIMITIVE_CONTAINER_TYPE)
+                        ->getFullyQualifiedNamespace(false);
+                }
             }
         } else if ($this->isResourceType()) {
             if (!$this->hasResourceTypeParent()) {
@@ -868,7 +884,7 @@ public function getDirectlyImplementedInterfaces(): array
                     ->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_RESOURCE_TYPE)
                     ->getFullyQualifiedNamespace(false);
             }
-        } else if (!$this->hasParent()) {
+        } else if (!$this->hasParent() && !$sourceMeta->isDSTU1()) {
             $interfaces[PHPFHIR_TYPES_INTERFACE_ELEMENT_TYPE] = $coreFiles
                 ->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_ELEMENT_TYPE)
                 ->getFullyQualifiedNamespace(false);
@@ -910,7 +926,7 @@ public function getDirectlyUsedTraits(): array
             }
 
             // these must only be added if the type has local properties
-            if ($this->isResourceType() && $this->hasLocalProperties()) {
+            if (($this->isResourceType() || $this->getVersion()->getSourceMetadata()->isDSTU1()) && $this->hasLocalProperties()) {
                 $traits[PHPFHIR_TRAIT_SOURCE_XMLNS] = $coreFiles
                     ->getCoreFileByEntityName(PHPFHIR_TRAIT_SOURCE_XMLNS)
                     ->getFullyQualifiedNamespace(false);
diff --git a/template/core/types/interface_dstu1_primitive_container_type.php b/template/core/types/interface_dstu1_primitive_container_type.php
new file mode 100644
index 00000000..b94cb017
--- /dev/null
+++ b/template/core/types/interface_dstu1_primitive_container_type.php
@@ -0,0 +1,71 @@
+<?php declare(strict_types=1);
+
+/*
+ * Copyright 2025 Daniel Carbone (daniel.p.carbone@gmail.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use DCarbone\PHPFHIR\Utilities\ImportUtils;
+
+/** @var \DCarbone\PHPFHIR\Config $config */
+/** @var \DCarbone\PHPFHIR\CoreFile $coreFile */
+
+$coreFiles = $config->getCoreFiles();
+
+$valueContainerInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_VALUE_CONTAINER_TYPE);
+$serializeConfigClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG);
+$xmlWriterClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_XML_WRITER);
+$xmlValueLocationEnum = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_ENUM_VALUE_XML_LOCATION);
+
+$imports = $coreFile->getimports();
+
+$imports->addCoreFileImports(
+    $valueContainerInterface,
+    $serializeConfigClass,
+    $xmlWriterClass,
+    $xmlValueLocationEnum,
+);
+
+ob_start();
+echo '<?php ';?>declare(strict_types=1);
+
+namespace <?php echo $coreFile->getFullyQualifiedNamespace(false); ?>;
+
+<?php echo $config->getBasePHPFHIRCopyrightComment(true); ?>
+
+<?php echo ImportUtils::compileImportStatements($imports); ?>
+
+interface <?php echo $coreFile->getEntityName(); ?> extends <?php echo $valueContainerInterface->getEntityName(); ?>
+
+{
+    /**
+     * Must return true if this primitive container type has a field set other than "value".  This is used during
+     * serialization.
+     *
+     * @return bool
+     */
+    public function _nonValueFieldDefined(): bool;
+
+    /**
+     * @param null|<?php echo $xmlWriterClass->getFullyQualifiedName(true); ?> $xw
+     * @param null|<?php echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
+     * @param null|<?php echo $xmlValueLocationEnum->getFullyQualifiedName(true); ?> $valueLocation
+     * @return <?php echo $xmlWriterClass->getFullyQualifiedName(true); ?>
+
+     */
+    public function xmlSerialize(null|<?php echo $xmlWriterClass->getEntityName(); ?> $xw,
+                                 null|<?php echo $serializeConfigClass->getEntityName(); ?> $config,
+                                 null|<?php echo $xmlValueLocationEnum->getEntityName(); ?> $valueLocation = null): <?php echo $xmlWriterClass->getEntityName() ?>;
+}
+<?php return ob_get_clean();
diff --git a/template/core/types/interface_dstu1_type.php b/template/core/types/interface_dstu1_type.php
index 0c68072d..062f87d5 100644
--- a/template/core/types/interface_dstu1_type.php
+++ b/template/core/types/interface_dstu1_type.php
@@ -23,14 +23,11 @@
 
 $coreFiles = $config->getCoreFiles();
 
-$typeInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_TYPE);
-$serializeConfigClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG);
-$unserializeConfigClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_UNSERIALIZE_CONFIG);
-$xmlWriterClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_XML_WRITER);
+$resourceTypeInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_RESOURCE_TYPE);
 
 $imports = $coreFile->getimports();
 
-$imports->addCoreFileImports($typeInterface, $serializeConfigClass, $unserializeConfigClass, $xmlWriterClass);
+$imports->addCoreFileImports($resourceTypeInterface);
 
 
 ob_start();
@@ -48,44 +45,9 @@
  * This is a special interface only applied when generating types for versions based on DSTU1.  It is necessary
  * as Resources in DSTU1 are extensions of Elements.  This is unique to DSTU1.
  */
-interface <?php echo $coreFile->getEntityName(); ?> extends <?php echo $typeInterface->getEntityName(); ?>, \JsonSerializable
-{
-    /**
-     * Returns the root XMLNS value found in the source.  Null indicates no "xmlns" was found.  Only defined when
-     * unserializing XML, and only used when serializing XML.
-     *
-     * @return null|string
-     */
-    public function _getSourceXMLNS(): null|string;
-
-    /**
-     * @param string|\SimpleXMLElement $element
-     * @param null|<?php echo $unserializeConfigClass->getFullyQualifiedName(true); ?> $config
-     * @param null|<?php echo $coreFile->getFullyQualifiedName(true); ?> $type Instance of this class to unserialize into.  If left null, a new instance will be created.
-     * @return static
-     */
-    public static function xmlUnserialize(string|\SimpleXMLElement $element,
-                                          null|<?php echo $unserializeConfigClass->getEntityName() ?> $config = null,
-                                          null|<?php echo $coreFile->getEntityName(); ?> $type = null): self;
-
-    /**
-     * @param null|<?php echo $xmlWriterClass->getFullyQualifiedName(true); ?> $xw
-     * @param null|<?php echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
-     * @return <?php echo $xmlWriterClass->getFullyQualifiedName(true); ?>
+interface <?php echo $coreFile->getEntityName(); ?> extends <?php echo $resourceTypeInterface->getEntityName(); ?>
 
-     */
-    public function xmlSerialize(null|<?php echo $xmlWriterClass->getEntityName(); ?> $xw = null,
-                                 null|<?php echo $serializeConfigClass->getEntityName(); ?> $config = null): <?php echo $xmlWriterClass->getEntityName(); ?>;
+{
 
-    /**
-     * @param string|array|\stdClass $json Raw or already un-encoded JSON
-     * @param null|<?php echo $unserializeConfigClass->getFullyQualifiedName(true); ?> $config
-     * @param null|<?php echo $coreFile->getFullyQualifiedName(true); ?> $type Instance of this class to unserialize into.  If left null, a new instance will be created.
-     * @return static
-     */
-    public static function jsonUnserialize(string|array|\stdClass $json,
-                                           null|<?php echo $unserializeConfigClass->getEntityName(); ?> $config = null,
-                                           null|<?php echo $coreFile->getEntityName(); ?> $type = null): self;
 }
-
 <?php return ob_get_clean();
diff --git a/template/core/types/interface_element_type.php b/template/core/types/interface_element_type.php
index a32d2711..3996de0d 100644
--- a/template/core/types/interface_element_type.php
+++ b/template/core/types/interface_element_type.php
@@ -71,5 +71,4 @@ public static function jsonUnserialize(array $json,
                                            <?php echo $unserializeConfigClass->getEntityName(); ?> $config,
                                            null|<?php echo $coreFile->getEntityName(); ?> $type = null): self;
 }
-
 <?php return ob_get_clean();
diff --git a/template/core/types/interface_primitive_container_type.php b/template/core/types/interface_primitive_container_type.php
index ddfcb6a8..cd3670ce 100644
--- a/template/core/types/interface_primitive_container_type.php
+++ b/template/core/types/interface_primitive_container_type.php
@@ -66,5 +66,4 @@ public function xmlSerialize(<?php echo $xmlWriterClass->getEntityName(); ?> $xw
                                  <?php echo $serializeConfigClass->getEntityName(); ?> $config,
                                  null|<?php echo $xmlValueLocationEnum->getEntityName(); ?> $valueLocation = null): void;
 }
-
 <?php return ob_get_clean();
diff --git a/template/core/types/interface_resource_type.php b/template/core/types/interface_resource_type.php
index e4d9232c..30efda3a 100644
--- a/template/core/types/interface_resource_type.php
+++ b/template/core/types/interface_resource_type.php
@@ -81,5 +81,4 @@ public static function jsonUnserialize(string|array|\stdClass $json,
                                            null|<?php echo $unserializeConfigClass->getEntityName(); ?> $config = null,
                                            null|<?php echo $coreFile->getEntityName(); ?> $type = null): self;
 }
-
 <?php return ob_get_clean();
diff --git a/template/core/types/interface_value_container_type.php b/template/core/types/interface_value_container_type.php
index af6bb6c1..86db92b3 100644
--- a/template/core/types/interface_value_container_type.php
+++ b/template/core/types/interface_value_container_type.php
@@ -36,5 +36,4 @@ interface <?php echo $coreFile->getEntityName(); ?>
      */
     public function _getFormattedValue(): string;
 }
-
 <?php return ob_get_clean();
diff --git a/template/core/types/trait_comment_container.php b/template/core/types/trait_comment_container.php
index 338c2cb6..8c0f3ff0 100644
--- a/template/core/types/trait_comment_container.php
+++ b/template/core/types/trait_comment_container.php
@@ -69,5 +69,4 @@ public function _addFHIRComment(string $fhirComment): self
         return $this;
     }
 }
-<?php
-return ob_get_clean();
+<?php return ob_get_clean();
diff --git a/template/versions/types/class_resource_container.php b/template/versions/types/class_resource_container.php
index d189dda2..c87805e6 100644
--- a/template/versions/types/class_resource_container.php
+++ b/template/versions/types/class_resource_container.php
@@ -130,7 +130,7 @@ public function setContainedType(null|<?php echo $versionContainedTypeInterface-
 
      */
     public function xmlSerialize(null|<?php echo $xmlWriterClass->getEntityName(); ?> $xw = null,
-                                 null|<?php echo $serializeConfigClass->getEntityName(); ?> $config = null): <?php echo $xmlWriterClass->getEntityName(); ?>;
+                                 null|<?php echo $serializeConfigClass->getEntityName(); ?> $config = null): <?php echo $xmlWriterClass->getEntityName(); ?>
 
     {
         $containedType = $this->getContainedType();
diff --git a/template/versions/types/header.php b/template/versions/types/header.php
index f5ef6953..67454670 100644
--- a/template/versions/types/header.php
+++ b/template/versions/types/header.php
@@ -50,9 +50,8 @@
 {<?php if ([] !== $traits) : ?>
 
     use <?php echo implode(",\n        ", array_keys($traits)); ?>;
-<?php endif; ?>
-
 
+<?php endif; ?>
     // name of FHIR type this class describes
     public const FHIR_TYPE_NAME = <?php echo $type->getTypeNameConst(true); ?>;
 
diff --git a/template/versions/types/serialization/json/unserialize/header.php b/template/versions/types/serialization/json/unserialize/header.php
index 1df14e39..d434e8d9 100644
--- a/template/versions/types/serialization/json/unserialize/header.php
+++ b/template/versions/types/serialization/json/unserialize/header.php
@@ -19,13 +19,15 @@
 /** @var \DCarbone\PHPFHIR\Version $version */
 /** @var \DCarbone\PHPFHIR\Version\Definition\Type $type */
 
+$sourceMeta = $version->getSourceMetadata();
+
 $config = $version->getConfig();
 
 $coreFiles = $config->getCoreFiles();
 $constantsClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_CLASSNAME_CONSTANTS);
 $unserializeConfigClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_UNSERIALIZE_CONFIG);
 
-if ($type->isResourceType() || $type->hasResourceTypeParent()) {
+if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) {
     $typeInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_RESOURCE_TYPE);
 } else {
     $typeInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_ELEMENT_TYPE);
@@ -36,15 +38,15 @@
 
 ob_start(); ?>
     /**
-     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>string|\stdClass|<?php endif; ?>array $json
-     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $unserializeConfigClass->getFullyQualifiedName(true); ?> $config
+     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>string|\stdClass|<?php endif; ?>array $json
+     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $unserializeConfigClass->getFullyQualifiedName(true); ?> $config
      * @param null|<?php echo $type->getFullyQualifiedClassName(true); ?> $type
      * @return <?php echo $type->getFullyQualifiedClassName(true); ?>
 
      * @throws \Exception
      */
-    public static function jsonUnserialize(<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>string|\stdClass|<?php endif; ?>array $json,
-                                           <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $unserializeConfigClass->getEntityName() ?> $config<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?> = null<?php endif;?>,
+    public static function jsonUnserialize(<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>string|\stdClass|<?php endif; ?>array $json,
+                                           <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $unserializeConfigClass->getEntityName() ?> $config<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?> = null<?php endif;?>,
                                            null|<?php echo $typeInterface->getEntityName(); ?> $type = null): self
     {
 <?php if ($type->isAbstract()) : // abstract types may not be instantiated directly ?>
@@ -61,7 +63,7 @@ public static function jsonUnserialize(<?php if ($type->isResourceType() || $typ
                 get_class($type)
             ));
         }
-<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>
+<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>
         if (null === $config) {
             $config = (new <?php echo $versionClass->getEntityName(); ?>())->getConfig()->getUnserializeConfig();
         }
diff --git a/template/versions/types/serialization/xml.php b/template/versions/types/serialization/xml.php
index c6fdce17..1a1e83d6 100644
--- a/template/versions/types/serialization/xml.php
+++ b/template/versions/types/serialization/xml.php
@@ -19,6 +19,8 @@
 /** @var \DCarbone\PHPFHIR\Version $version */
 /** @var \DCarbone\PHPFHIR\Version\Definition\Type $type; */
 
+$sourceMeta = $version->getSourceMetadata();
+
 $typeKind = $type->getKind();
 
 ob_start();
@@ -66,7 +68,7 @@
         ]
     );
 
-    if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>
+    if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>
         if (isset($rootOpened) && $rootOpened) {
             $xw->endElement();
         }
diff --git a/template/versions/types/serialization/xml/serialize/header.php b/template/versions/types/serialization/xml/serialize/header.php
index 87ec7e10..7882c390 100644
--- a/template/versions/types/serialization/xml/serialize/header.php
+++ b/template/versions/types/serialization/xml/serialize/header.php
@@ -21,6 +21,8 @@
 /** @var \DCarbone\PHPFHIR\Version $version */
 /** @var \DCarbone\PHPFHIR\Version\Definition\Type $type */
 
+$sourceMeta = $version->getSourceMetadata();
+
 $config = $version->getConfig();
 
 $coreFiles = $config->getCoreFiles();
@@ -33,23 +35,23 @@
 
 ob_start(); ?>
     /**
-     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $xmlWriterClass->getFullyQualifiedName(true); ?> $xw
-     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
+     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $xmlWriterClass->getFullyQualifiedName(true); ?> $xw
+     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
 <?php if ($type->isPrimitiveContainer() || $type->hasPrimitiveContainerParent()) : ?>
      * @param null|<?php echo $xmlLocationEnum->getFullyQualifiedName(true); ?> $valueLocation
 <?php endif; ?>
-<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>
+<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>
      * @return <?php echo $xmlWriterClass->getFullyQualifiedName(true); ?>
 
 <?php endif; ?>
      */
-    public function xmlSerialize(<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif;  echo $xmlWriterClass->getEntityName(); ?> $xw<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?> = null<?php endif; ?>,
-                                 <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $serializeConfigClass->getEntityName(); ?> $config<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?> = null<?php endif;
+    public function xmlSerialize(<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif;  echo $xmlWriterClass->getEntityName(); ?> $xw<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?> = null<?php endif; ?>,
+                                 <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $serializeConfigClass->getEntityName(); ?> $config<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?> = null<?php endif;
     if ($type->isPrimitiveContainer() || $type->hasPrimitiveContainerParent()) : ?>,
-                                 null|<?php echo $xmlLocationEnum->getEntityName(); ?> $valueLocation = null<?php endif; ?>): <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : echo $xmlWriterClass->getEntityName(); else : ?>void<?php endif; ?>
+                                 null|<?php echo $xmlLocationEnum->getEntityName(); ?> $valueLocation = null<?php endif; ?>): <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : echo $xmlWriterClass->getEntityName(); else : ?>void<?php endif; ?>
 
     {
-<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>
+<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>
         if (null === $config) {
             $config = (new <?php echo $versionClass->getEntityName(); ?>())->getConfig()->getSerializeConfig();
         }
diff --git a/template/versions/types/serialization/xml/unserialize/header.php b/template/versions/types/serialization/xml/unserialize/header.php
index 60d8de02..0aa0b0c9 100644
--- a/template/versions/types/serialization/xml/unserialize/header.php
+++ b/template/versions/types/serialization/xml/unserialize/header.php
@@ -19,12 +19,14 @@
 /** @var \DCarbone\PHPFHIR\Version $version */
 /** @var \DCarbone\PHPFHIR\Version\Definition\Type $type */
 
+$sourceMeta = $version->getSourceMetadata();
+
 $config = $version->getConfig();
 
 $coreFiles = $config->getCoreFiles();
 $unserializeConfigClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_UNSERIALIZE_CONFIG);
 
-if ($type->isResourceType() || $type->hasResourceTypeParent()) {
+if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) {
     $typeInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_RESOURCE_TYPE);
 } else {
     $typeInterface = $coreFiles->getCoreFileByEntityName(PHPFHIR_TYPES_INTERFACE_ELEMENT_TYPE);
@@ -35,15 +37,15 @@
 
 ob_start(); ?>
     /**
-     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>string|<?php endif; ?>\SimpleXMLElement $element
-     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $unserializeConfigClass->getFullyQualifiedName(true); ?> $config
+     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>string|<?php endif; ?>\SimpleXMLElement $element
+     * @param <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $unserializeConfigClass->getFullyQualifiedName(true); ?> $config
      * @param null|<?php echo $type->getFullyQualifiedClassName(true); ?> $type
      * @return <?php echo $type->getFullyQualifiedClassName(true); ?>
 
      * @throws \Exception
      */
-    public static function xmlUnserialize(<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>string|<?php endif; ?>\SimpleXMLElement $element,
-                                          <?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>null|<?php endif; echo $unserializeConfigClass->getEntityName() ?> $config<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?> = null<?php endif;?>,
+    public static function xmlUnserialize(<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>string|<?php endif; ?>\SimpleXMLElement $element,
+                                          <?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>null|<?php endif; echo $unserializeConfigClass->getEntityName() ?> $config<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?> = null<?php endif;?>,
                                           null|<?php echo $typeInterface->getEntityName(); ?> $type = null): self
     {
 <?php if ($type->isAbstract()) : // abstract types may not be instantiated directly ?>
@@ -60,7 +62,7 @@ public static function xmlUnserialize(<?php if ($type->isResourceType() || $type
                 get_class($type)
             ));
         }
-<?php if ($type->isResourceType() || $type->hasResourceTypeParent()) : ?>
+<?php if ($type->isResourceType() || $type->hasResourceTypeParent() || $sourceMeta->isDSTU1()) : ?>
         if (null === $config) {
             $config = (new <?php echo $versionClass->getEntityName(); ?>())->getConfig()->getUnserializeConfig();
         }