diff --git a/core/ClassInfo.php b/core/ClassInfo.php
index 7aa17fa56..9c0f845fc 100644
--- a/core/ClassInfo.php
+++ b/core/ClassInfo.php
@@ -58,8 +58,10 @@ class ClassInfo {
 	 * Returns the manifest of all classes which are present in the database.
 	 * @param string $class Class name to check enum values for ClassName field
 	 */
-	static function getValidSubClasses($class = 'SiteTree') {
-		return DB::getConn()->enumValuesForField($class, 'ClassName');
+	static function getValidSubClasses($class = 'SiteTree', $includeUnbacked = false) {
+		$classes = DB::getConn()->enumValuesForField($class, 'ClassName');
+		if (!$includeUnbacked) $classes = array_filter($classes, array('ClassInfo', 'exists'));
+		return $classes;
 	}
 
 	/**
diff --git a/model/DataObject.php b/model/DataObject.php
index e624a794d..cbfa2876f 100644
--- a/model/DataObject.php
+++ b/model/DataObject.php
@@ -181,9 +181,12 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 	 */
 	public static function database_fields($class) {
 		if(get_parent_class($class) == 'DataObject') {
+			$db = DB::getConn();
+			$existing = $db->hasField($class, 'ClassName') ? $db->query("SELECT DISTINCT \"ClassName\" FROM \"$class\"")->column() : array();
+
 			return array_merge (
 				array (
-					'ClassName'  => "Enum('" . implode(', ', ClassInfo::subclassesFor($class)) . "')",
+					'ClassName'  => "Enum('" . implode(', ', array_unique(array_merge($existing, ClassInfo::subclassesFor($class)))) . "')",
 					'Created'    => 'SS_Datetime',
 					'LastEdited' => 'SS_Datetime'
 				),
@@ -443,6 +446,17 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 			}
 		}
 	}
+
+	function getObsoleteClassName() {
+		$className = $this->getField("ClassName");
+		if (!ClassInfo::exists($className)) return $className;
+	}
+
+	function getClassName() {
+		$className = $this->getField("ClassName");
+		if (!ClassInfo::exists($className)) return get_class($this);
+		return $className;
+	}
 	
 	/**
 	 * Set the ClassName attribute. {@link $class} is also updated.
@@ -985,17 +999,34 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 		$firstWrite = false;
 		$this->brokenOnWrite = true;
 		$isNewRecord = false;
-		
-		if(self::get_validation_enabled()) {
+
+		$writeException = null;
+
+		if ($this->ObsoleteClassName) {
+			$writeException = new ValidationException(
+				"Object is of class '{$this->ObsoleteClassName}' which doesn't exist - ".
+				"you need to change the ClassName before you can write it",
+				E_USER_WARNING
+			);
+		}
+		else if(self::get_validation_enabled()) {
 			$valid = $this->validate();
-			if(!$valid->valid()) {
-				// Used by DODs to clean up after themselves, eg, Versioned
-				$this->extend('onAfterSkippedWrite');
-				throw new ValidationException($valid, "Validation error writing a $this->class object: " . $valid->message() . ".  Object not written.", E_USER_WARNING);
-				return false;
+			if (!$valid->valid()) {
+				$writeException = new ValidationException(
+					$valid,
+					"Validation error writing a $this->class object: " . $valid->message() . ".  Object not written.",
+					E_USER_WARNING
+				);
 			}
 		}
 
+		if($writeException) {
+			// Used by DODs to clean up after themselves, eg, Versioned
+			$this->extend('onAfterSkippedWrite');
+			throw $writeException;
+			return false;
+		}
+
 		$this->onBeforeWrite();
 		if($this->brokenOnWrite) {
 			user_error("$this->class has a broken onBeforeWrite() function.  Make sure that you call parent::onBeforeWrite().", E_USER_ERROR);
diff --git a/model/Database.php b/model/Database.php
index d76f73853..7e32cd114 100644
--- a/model/Database.php
+++ b/model/Database.php
@@ -143,7 +143,7 @@ abstract class SS_Database {
 	 * Returns true if the given table exists in the database
 	 */
 	abstract function hasTable($tableName);
-	
+
 	/**
 	 * Returns the enum values available on the given field
 	 */
@@ -439,6 +439,18 @@ abstract class SS_Database {
 		}
 	}
 
+	/**
+	 * Return true if the table exists and already has a the field specified
+	 * @param string $tableName - The table to check
+	 * @param string $fieldName - The field to check
+	 * @return bool - True if the table exists and the field exists on the table
+	 */
+	function hasField($tableName, $fieldName) {
+		if (!$this->hasTable($tableName)) return false;
+		$fields = $this->fieldList($tableName);
+		return array_key_exists($fieldName, $fields);
+	}
+
 	/**
 	 * Generate the given field on the table, modifying whatever already exists as necessary.
 	 * @param string $table The table name.
diff --git a/model/Versioned.php b/model/Versioned.php
index 25da1a7c4..b8efd4d87 100644
--- a/model/Versioned.php
+++ b/model/Versioned.php
@@ -1103,7 +1103,7 @@ class Versioned_Version extends ViewableData {
 		$record['ID'] = $record['RecordID'];
 		$className = $record['ClassName'];
 		
-		$this->object = new $className($record);
+		$this->object = ClassInfo::exists($className) ? new $className($record) : new DataObject($record);
 		$this->failover = $this->object;
 		
 		parent::__construct();