diff --git a/modules/backend/formwidgets/Relation.php b/modules/backend/formwidgets/Relation.php
index 3dc4e4f9e..f59f309ce 100644
--- a/modules/backend/formwidgets/Relation.php
+++ b/modules/backend/formwidgets/Relation.php
@@ -139,9 +139,15 @@ class Relation extends FormWidgetBase
                 $result = $query->getQuery()->get();
             }
 
+            // Some simpler relations can specify a custom local or foreign "other" key,
+            // which can be detected and implemented here automagically.
+            $primaryKeyName = in_array($relationType, ['hasMany', 'belongsTo', 'hasOne'])
+                ? $relationObject->getOtherKey()
+                : $relationModel->getKeyName();
+
             $field->options = $usesTree
-                ? $result->listsNested($nameFrom, $relationObject->getOtherKey())
-                : $result->lists($nameFrom, $relationObject->getOtherKey());
+                ? $result->listsNested($nameFrom, $primaryKeyName)
+                : $result->lists($nameFrom, $primaryKeyName);
 
             return $field;
         });