diff --git a/modules/backend/behaviors/RelationController.php b/modules/backend/behaviors/RelationController.php
index a2813d876..de09b21fe 100644
--- a/modules/backend/behaviors/RelationController.php
+++ b/modules/backend/behaviors/RelationController.php
@@ -913,6 +913,19 @@ class RelationController extends ControllerBehavior
 
         if ($this->viewMode == 'multi') {
             $newModel = $this->relationModel;
+
+            /*
+             * In special cases, has one/many will require a foreign key set
+             * to pass any constraints imposed by the database. This emulates
+             * the "create" method on the relation object.
+             */
+            if (in_array($this->relationType, ['hasOne', 'hasMany'])) {
+                $newModel->setAttribute(
+                    $this->relationObject->getPlainForeignKey(),
+                    $this->relationObject->getParentKey()
+                );
+            }
+
             $modelsToSave = $this->prepareModelsToSave($newModel, $saveData);
             foreach ($modelsToSave as $modelToSave) {
                 $modelToSave->save(null, $this->manageWidget->getSessionKey());