diff --git a/src/DataFormatter.php b/src/DataFormatter.php
index 246ca34..2e2ace6 100644
--- a/src/DataFormatter.php
+++ b/src/DataFormatter.php
@@ -301,7 +301,9 @@ abstract class DataFormatter
         if (is_array($this->customFields)) {
             foreach ($this->customFields as $fieldName) {
                 // @todo Possible security risk by making methods accessible - implement field-level security
-                if ($obj->hasField($fieldName) || $obj->hasMethod("get{$fieldName}")) {
+                if (($obj->hasField($fieldName) && !is_object($obj->getField($fieldName)))
+                    || $obj->hasMethod("get{$fieldName}")
+                ) {
                     $dbFields[$fieldName] = $fieldName;
                 }
             }
diff --git a/tests/unit/Stubs/RestfulServerTestAuthor.php b/tests/unit/Stubs/RestfulServerTestAuthor.php
index 8f16a07..0145f03 100644
--- a/tests/unit/Stubs/RestfulServerTestAuthor.php
+++ b/tests/unit/Stubs/RestfulServerTestAuthor.php
@@ -2,11 +2,8 @@
 
 namespace SilverStripe\RestfulServer\Tests\Stubs;
 
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestPage;
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestAuthor;
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestAuthorRating;
-use SilverStripe\ORM\DataObject;
 use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
 
 class RestfulServerTestAuthor extends DataObject implements TestOnly
 {
diff --git a/tests/unit/Stubs/RestfulServerTestAuthorRating.php b/tests/unit/Stubs/RestfulServerTestAuthorRating.php
index 87f2500..79300d6 100644
--- a/tests/unit/Stubs/RestfulServerTestAuthorRating.php
+++ b/tests/unit/Stubs/RestfulServerTestAuthorRating.php
@@ -2,9 +2,8 @@
 
 namespace SilverStripe\RestfulServer\Tests\Stubs;
 
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestAuthor;
-use SilverStripe\ORM\DataObject;
 use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
 
 class RestfulServerTestAuthorRating extends DataObject implements TestOnly
 {
diff --git a/tests/unit/Stubs/RestfulServerTestComment.php b/tests/unit/Stubs/RestfulServerTestComment.php
index c780003..349b01c 100644
--- a/tests/unit/Stubs/RestfulServerTestComment.php
+++ b/tests/unit/Stubs/RestfulServerTestComment.php
@@ -2,12 +2,10 @@
 
 namespace SilverStripe\RestfulServer\Tests\Stubs;
 
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestPage;
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestAuthor;
-use SilverStripe\Security\Permission;
-use SilverStripe\ORM\DataObject;
-use SilverStripe\Security\PermissionProvider;
 use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
+use SilverStripe\Security\Permission;
+use SilverStripe\Security\PermissionProvider;
 
 /**
  * Everybody can view comments, logged in members in the "users" group can create comments,
diff --git a/tests/unit/Stubs/RestfulServerTestPage.php b/tests/unit/Stubs/RestfulServerTestPage.php
index 7c3a725..774d450 100644
--- a/tests/unit/Stubs/RestfulServerTestPage.php
+++ b/tests/unit/Stubs/RestfulServerTestPage.php
@@ -2,10 +2,8 @@
 
 namespace SilverStripe\RestfulServer\Tests\Stubs;
 
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestAuthor;
-use SilverStripe\RestfulServer\Tests\Stubs\RestfulServerTestComment;
-use SilverStripe\ORM\DataObject;
 use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
 
 class RestfulServerTestPage extends DataObject implements TestOnly
 {
diff --git a/tests/unit/Stubs/RestfulServerTestSecretThing.php b/tests/unit/Stubs/RestfulServerTestSecretThing.php
index 8faec95..2a87239 100644
--- a/tests/unit/Stubs/RestfulServerTestSecretThing.php
+++ b/tests/unit/Stubs/RestfulServerTestSecretThing.php
@@ -2,9 +2,9 @@
 
 namespace SilverStripe\RestfulServer\Tests\Stubs;
 
-use SilverStripe\Security\Permission;
-use SilverStripe\ORM\DataObject;
 use SilverStripe\Dev\TestOnly;
+use SilverStripe\ORM\DataObject;
+use SilverStripe\Security\Permission;
 use SilverStripe\Security\PermissionProvider;
 
 class RestfulServerTestSecretThing extends DataObject implements TestOnly, PermissionProvider