diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index c2347b4..4c63ce0 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -1049,11 +1049,13 @@ protected function beforeInsertNode(int|null $value, int $depth): void
             throw new Exception('Can not create a node when the target node is root.');
         }
 
-        if ($value !== null) {
-            $this->getOwner()->setAttribute($this->leftAttribute, $value);
-            $this->getOwner()->setAttribute($this->rightAttribute, $value + 1);
+        if ($value === null) {
+            throw new Exception('Value cannot be \'null\' in \'beforeInsertNode()\' method.');
         }
 
+        $this->getOwner()->setAttribute($this->leftAttribute, $value);
+        $this->getOwner()->setAttribute($this->rightAttribute, $value + 1);
+
         $nodeDepthValue = $this->node?->getAttribute($this->depthAttribute) ?? 0;
 
         $this->getOwner()->setAttribute($this->depthAttribute, $nodeDepthValue + $depth);
@@ -1062,7 +1064,7 @@ protected function beforeInsertNode(int|null $value, int $depth): void
             $this->getOwner()->setAttribute($this->treeAttribute, $this->node->getAttribute($this->treeAttribute));
         }
 
-        $this->shiftLeftRightAttribute($value ?? 0, 2);
+        $this->shiftLeftRightAttribute($value, 2);
     }
 
     /**
diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index 4553b45..d24645f 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1719,4 +1719,21 @@ public function testAppendChildNodeToRootCreatesValidTreeStructure(): void
             self::fail('Real insertion failed: ' . $e->getMessage());
         }
     }
+
+    public function testThrowExceptionWhenAppendToParentWithNullRightValue(): void
+    {
+        $this->createDatabase();
+
+        $parentNode = new Tree(['name' => 'Parent Node']);
+
+        $parentNode->makeRoot();
+        $parentNode->setAttribute('rgt', null);
+
+        $childNode = new Tree(['name' => 'Child Node']);
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('Value cannot be \'null\' in \'beforeInsertNode()\' method.');
+
+        $childNode->appendTo($parentNode);
+    }
 }