diff --git a/src/Forms/RequiredFields.php b/src/Forms/RequiredFields.php
index 918a32a1121..9b684cc63ce 100644
--- a/src/Forms/RequiredFields.php
+++ b/src/Forms/RequiredFields.php
@@ -104,10 +104,18 @@ public function php($data)
                 $fieldName = $fieldName->getName();
             } else {
                 $formField = $fields->dataFieldByName($fieldName);
+                if (is_null($formField)) {
+                    $formField = $fields->dataFieldByName($fieldName . 'ID');
+                }
             }
 
             // submitted data for file upload fields come back as an array
-            $value = isset($data[$fieldName]) ? $data[$fieldName] : null;
+            $value = null;
+            if (isset($data[$fieldName])) {
+                $value = $data[$fieldName];
+            } elseif (isset($data[$fieldName . 'ID'])) {
+                $value = $data[$fieldName . 'ID'];
+            }
 
             if (is_array($value)) {
                 if ($formField instanceof FileField && isset($value['error']) && $value['error']) {
diff --git a/src/Forms/SearchableDropdownField.php b/src/Forms/SearchableDropdownField.php
index 901a88739ec..6d01feb8237 100644
--- a/src/Forms/SearchableDropdownField.php
+++ b/src/Forms/SearchableDropdownField.php
@@ -5,8 +5,9 @@
 use SilverStripe\Dev\Deprecation;
 use SilverStripe\Forms\DropdownField;
 use SilverStripe\ORM\DataList;
+use SilverStripe\Forms\HasOneRelationFieldInterface;
 
-class SearchableDropdownField extends DropdownField
+class SearchableDropdownField extends DropdownField implements HasOneRelationFieldInterface
 {
     use SearchableDropdownTrait;
     
diff --git a/tests/php/Forms/RequiredFieldsTest.php b/tests/php/Forms/RequiredFieldsTest.php
index 7da79eda213..997c826725f 100644
--- a/tests/php/Forms/RequiredFieldsTest.php
+++ b/tests/php/Forms/RequiredFieldsTest.php
@@ -5,6 +5,7 @@
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Forms\RequiredFields;
 use SilverStripe\Forms\Form;
+use SilverStripe\Forms\SearchableDropdownField;
 use SilverStripe\Forms\TreeDropdownField;
 use SilverStripe\Security\Group;
 
@@ -289,17 +290,24 @@ public function testFieldIsRequired()
         );
     }
 
-    public function testTreedropFieldValidation()
+    public function testHasOneRelationFieldInterfaceValidation()
     {
-        $form = new Form();
-        $field = new TreeDropdownField('TestField', 'TestField', Group::class);
-        $form->Fields()->push($field);
-        $validator = new RequiredFields('TestField');
-        $validator->setForm($form);
-        // blank string and '0' are fail required field validation
-        $this->assertFalse($validator->php(['TestField' => '']));
-        $this->assertFalse($validator->php(['TestField' => '0']));
-        // '1' passes required field validation
-        $this->assertTrue($validator->php(['TestField' => '1']));
+        $fieldClasses = [TreeDropdownField::class, SearchableDropdownField::class];
+        $suffixes = ['', 'ID'];
+        foreach ($fieldClasses as $fieldClass) {
+            foreach ($suffixes as $suffix) {
+                $form = new Form();
+                $param = $fieldClass === TreeDropdownField::class ? Group::class : Group::get();
+                $field = new $fieldClass('TestField' . $suffix, 'TestField', $param);
+                $form->Fields()->push($field);
+                $validator = new RequiredFields('TestField');
+                $validator->setForm($form);
+                // blank string and '0' are fail required field validation
+                $this->assertFalse($validator->php(['TestField' => '']));
+                $this->assertFalse($validator->php(['TestField' => '0']));
+                // '1' passes required field validation
+                $this->assertTrue($validator->php(['TestField' => '1']));
+            }
+        }
     }
 }