diff --git a/src/GridFieldOrderableRows.php b/src/GridFieldOrderableRows.php
index 91cb6d3..d660fe2 100755
--- a/src/GridFieldOrderableRows.php
+++ b/src/GridFieldOrderableRows.php
@@ -18,8 +18,10 @@ use SilverStripe\ORM\DB;
 use SilverStripe\ORM\DataList;
 use SilverStripe\ORM\DataObjectInterface;
 use SilverStripe\ORM\ManyManyList;
+use SilverStripe\ORM\Map;
 use SilverStripe\ORM\SS_List;
 use SilverStripe\ORM\SS_Map;
+use SilverStripe\Versioned\Versioned;
 use SilverStripe\View\ViewableData;
 use Exception;
 
@@ -171,12 +173,6 @@ class GridFieldOrderableRows extends RequestHandler implements
         return $this;
     }
 
-    /**
-     * Gets the table which contains the sort field.
-     *
-     * @param DataList $list
-     * @return string
-     */
     public function getSortTable(SS_List $list)
     {
         $field = $this->getSortField();
@@ -189,12 +185,23 @@ class GridFieldOrderableRows extends RequestHandler implements
                 return $table;
             }
         }
+        return DataObject::getSchema()->tableName($this->getSortTableClass($list));
+    }
 
+    /**
+     * Gets the class which contains the sort field.
+     *
+     * @param DataList $list
+     * @return string
+     */
+    public function getSortTableClass(SS_List $list)
+    {
+        $field = $this->getSortField();
         $classes = ClassInfo::dataClassesFor($list->dataClass());
 
         foreach ($classes as $class) {
             if (singleton($class)->hasDataBaseField($field)) {
-                return DataObject::getSchema()->tableName($class);
+                return $class;
             }
         }
 
@@ -499,15 +506,15 @@ class GridFieldOrderableRows extends RequestHandler implements
         /** @var SS_List $map */
         $map = $list->map('ID', $sortField);
         //fix for versions of SS that return inconsistent types for `map` function
-        if ($map instanceof SS_Map) {
+        if ($map instanceof Map) {
             $map = $map->toArray();
         }
 
         // If not a ManyManyList and using versioning, detect it.
         $isVersioned = false;
         $class = $list->dataClass();
-        if ($class == $this->getSortTable($list)) {
-            $isVersioned = $class::has_extension('SilverStripe\\ORM\\Versioning\\Versioned');
+        if ($class == $this->getSortTableClass($list)) {
+            $isVersioned = $class::has_extension(Versioned::class);
         }
 
         // Loop through each item, and update the sort values which do not