diff --git a/Models/Department.php b/Models/Department.php
index f099582..86d06d6 100755
--- a/Models/Department.php
+++ b/Models/Department.php
@@ -145,8 +145,8 @@ class Department implements \JsonSerializable, ArrayableInterface
             'status'         => $this->status,
             'description'    => $this->description,
             'descriptionRaw' => $this->descriptionRaw,
-            'unit'           => $this->unit ?? new NullUnit(),
-            'parent'         => $this->parent ?? new NullDepartment(),
+            'unit'           => $this->unit,
+            'parent'         => $this->parent ?? null,
         ];
     }
 
diff --git a/Models/Position.php b/Models/Position.php
index 11aa19d..60d9061 100755
--- a/Models/Position.php
+++ b/Models/Position.php
@@ -143,7 +143,7 @@ class Position implements \JsonSerializable, ArrayableInterface
             'description'    => $this->description,
             'descriptionRaw' => $this->descriptionRaw,
             'department'     => $this->department ?? new NullDepartment(),
-            'parent'         => $this->parent ?? new NullPosition(),
+            'parent'         => $this->parent ?? null,
         ];
     }
 
diff --git a/Models/Unit.php b/Models/Unit.php
index d6fab4b..26dc583 100755
--- a/Models/Unit.php
+++ b/Models/Unit.php
@@ -144,7 +144,7 @@ class Unit implements \JsonSerializable, ArrayableInterface
             'status'         => $this->status,
             'description'    => $this->description,
             'descriptionRaw' => $this->descriptionRaw,
-            'parent'         => $this->parent,
+            'parent'         => $this->parent ?? null,
             'image'          => $this->image,
         ];
     }
diff --git a/Theme/Backend/organigram.tpl.php b/Theme/Backend/organigram.tpl.php
index e6c7e82..d197b0b 100755
--- a/Theme/Backend/organigram.tpl.php
+++ b/Theme/Backend/organigram.tpl.php
@@ -87,8 +87,8 @@ $unitRoot = $unitTree[null][0]['children'];
 
                                         do {
                                             ++$toCloseDep;
-                                            $parentDep   = $parentDep->parent;
-                                            $parentDepId = $parentDep->getId();
+                                            $parentDep   = $parentDep->parent ?? null;
+                                            $parentDepId = $parentDep?->getId() ?? 0;
                                         } while ($parentDepId !== 0
                                             && !isset($depTree[$unitId][$parentDepId]['children'][($depTree[$unitId][$parentDepId]['index'] ?? 0) + 1])
                                         );