diff --git a/src/ORM/DataObject.php b/src/ORM/DataObject.php
index 30d2c426d..8a8069bf1 100644
--- a/src/ORM/DataObject.php
+++ b/src/ORM/DataObject.php
@@ -2370,8 +2370,8 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
      */
     public function getField($field)
     {
-        // If we already have an object in $this->record, then we should just return that
-        if (isset($this->record[$field]) && is_object($this->record[$field])) {
+        // If we already have a value in $this->record, then we should just return that
+        if (isset($this->record[$field])) {
             return $this->record[$field];
         }
 
@@ -2591,13 +2591,15 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
         // Support component assignent via field setter
         $schema = static::getSchema();
         if ($schema->unaryComponent(static::class, $fieldName)) {
+            unset($this->components[$fieldName]);
             // Assign component directly
             if (is_null($val) || $val instanceof DataObject) {
                 return $this->setComponent($fieldName, $val);
             }
             // Assign by ID instead of object
-            unset($this->components[$fieldName]);
-            $fieldName .= 'ID';
+            if (is_numeric($val)) {
+                $fieldName .= 'ID';
+            }
         }
 
         // Situation 1: Passing an DBField
diff --git a/tests/php/ORM/DataObjectTest.php b/tests/php/ORM/DataObjectTest.php
index ab37a6e80..606075f5b 100644
--- a/tests/php/ORM/DataObjectTest.php
+++ b/tests/php/ORM/DataObjectTest.php
@@ -673,6 +673,31 @@ class DataObjectTest extends SapphireTest
         );
     }
 
+    /**
+     * Test has_one used as field getter/setter
+     */
+    public function testHasOneAsField()
+    {
+        /** @var DataObjectTest\Team $team1 */
+        $team1 = $this->objFromFixture(DataObjectTest\Team::class, 'team1');
+        $captain1 = $this->objFromFixture(DataObjectTest\Player::class, 'captain1');
+        $captain2 = $this->objFromFixture(DataObjectTest\Player::class, 'captain2');
+
+        // Setter: By RelationID
+        $team1->CaptainID = $captain1->ID;
+        $team1->write();
+        $this->assertEquals($captain1->ID, $team1->Captain->ID);
+
+        // Setter: New object
+        $team1->Captain = $captain2;
+        $team1->write();
+        $this->assertEquals($captain2->ID, $team1->Captain->ID);
+
+        // Setter: Custom data (required by DataDifferencer)
+        $team1->Captain = DBField::create_field('HTMLFragment', '<p>No captain</p>');
+        $this->assertEquals('<p>No captain</p>', $team1->Captain);
+    }
+
     /**
      * @todo Extend type change tests (e.g. '0'==NULL)
      */