diff --git a/src/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor.php b/src/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor.php
new file mode 100644
index 00000000000..5664082e8eb
--- /dev/null
+++ b/src/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor.php
@@ -0,0 +1,65 @@
+<?php declare(strict_types=1);
+
+namespace Rector\NodeVisitor\UpgradeDeprecation;
+
+use PhpParser\Node;
+use PhpParser\Node\Name\FullyQualified;
+use PhpParser\Node\Stmt\TraitUse;
+use PhpParser\NodeTraverser;
+use PhpParser\NodeVisitorAbstract;
+
+/**
+ * Reflects @link https://doc.nette.org/en/2.4/migration-2-4#toc-nette-smartobject
+ */
+final class DeprecatedParentClassToTraitNodeVisitor extends NodeVisitorAbstract
+{
+    public function getParentClassName(): string
+    {
+        return 'Nette\Object';
+    }
+
+    public function getTraitName(): string
+    {
+        return 'Nette\SmartObject';
+    }
+
+    public function enterNode(Node $node): ?int
+    {
+        if ($this->isCandidate($node)) {
+            $this->refactor($node);
+            return NodeTraverser::DONT_TRAVERSE_CHILDREN;
+        }
+
+        return null;
+    }
+
+    private function isCandidate(Node $node): bool
+    {
+        if ($node instanceof Node\Stmt\Class_) {
+            if (! $node->extends) {
+                return false;
+            }
+
+            $parentClassName = (string) $node->extends;
+            if ($parentClassName !== $this->getParentClassName()) {
+                return false;
+            }
+
+            return true;
+        }
+
+        return false;
+    }
+
+    private function refactor(Node\Stmt\Class_ $classNode)
+    {
+        // remove parent class
+        $classNode->extends = null;
+
+        // add new trait
+        $nameParts = explode('\\', $this->getTraitName());
+        $classNode->stmts[] = new TraitUse([
+            new FullyQualified($nameParts)
+        ]);
+    }
+}
diff --git a/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/Test.php b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/Test.php
new file mode 100644
index 00000000000..a7a8f29ac9a
--- /dev/null
+++ b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/Test.php
@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Tests\NodeVisitor\UpgradeDeprecation\DeprecatedParentClassToTraitNodeVisitor;
+
+use Rector\Testing\PHPUnit\AbstractReconstructorTestCase;
+
+final class Test extends AbstractReconstructorTestCase
+{
+    public function test(): void
+    {
+        $this->doTestFileMatchesExpectedContent(
+            __DIR__ . '/wrong/wrong.php.inc',
+            __DIR__ . '/correct/correct.php.inc'
+        );
+    }
+}
diff --git a/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/correct/correct.php.inc b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/correct/correct.php.inc
new file mode 100644
index 00000000000..10e922d412f
--- /dev/null
+++ b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/correct/correct.php.inc
@@ -0,0 +1,6 @@
+<?php declare (strict_types=1);
+
+class ClassWithExternalConstant
+{
+    use \Nette\SmartObject;
+}
diff --git a/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/correct/correct2.php.inc b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/correct/correct2.php.inc
new file mode 100644
index 00000000000..9444ca901f4
--- /dev/null
+++ b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/correct/correct2.php.inc
@@ -0,0 +1,7 @@
+<?php declare (strict_types=1);
+
+class ClassWithExternalConstant
+{
+    use \Nette\SmartObject;
+    use AnotherTrait;
+}
diff --git a/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/wrong/wrong.php.inc b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/wrong/wrong.php.inc
new file mode 100644
index 00000000000..80380536187
--- /dev/null
+++ b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/wrong/wrong.php.inc
@@ -0,0 +1,5 @@
+<?php declare (strict_types=1);
+
+class ClassWithExternalConstant extends Nette\Object
+{
+}
diff --git a/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/wrong/wrong2.php.inc b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/wrong/wrong2.php.inc
new file mode 100644
index 00000000000..4fa98fdeb8d
--- /dev/null
+++ b/tests/NodeVisitor/UpgradeDeprecation/DeprecatedParentClassToTraitNodeVisitor/wrong/wrong2.php.inc
@@ -0,0 +1,6 @@
+<?php declare (strict_types=1);
+
+class ClassWithExternalConstant extends Nette\Object
+{
+    use AnotherTrait;
+}