diff --git a/src/PhpSpreadsheet/Spreadsheet.php b/src/PhpSpreadsheet/Spreadsheet.php
index 364700e25..db43d558f 100644
--- a/src/PhpSpreadsheet/Spreadsheet.php
+++ b/src/PhpSpreadsheet/Spreadsheet.php
@@ -2,6 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheet;
 
+use JsonSerializable;
 use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
 use PhpOffice\PhpSpreadsheet\Reader\Xlsx as XlsxReader;
 use PhpOffice\PhpSpreadsheet\Shared\File;
@@ -11,7 +12,7 @@ use PhpOffice\PhpSpreadsheet\Worksheet\Iterator;
 use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use PhpOffice\PhpSpreadsheet\Writer\Xlsx as XlsxWriter;
 
-class Spreadsheet
+class Spreadsheet implements JsonSerializable
 {
     // Allowable values for workbook window visilbity
     const VISIBILITY_VISIBLE = 'visible';
@@ -1637,4 +1638,22 @@ class Spreadsheet
     {
         return new Style();
     }
+
+    /**
+     * @throws Exception
+     *
+     * @return mixed
+     */
+    public function __serialize()
+    {
+        throw new Exception('Spreadsheet objects cannot be serialized');
+    }
+
+    /**
+     * @throws Exception
+     */
+    public function jsonSerialize(): mixed
+    {
+        throw new Exception('Spreadsheet objects cannot be json encoded');
+    }
 }
diff --git a/tests/PhpSpreadsheetTests/SpreadsheetTest.php b/tests/PhpSpreadsheetTests/SpreadsheetTest.php
index 76e28b3db..19fb182f4 100644
--- a/tests/PhpSpreadsheetTests/SpreadsheetTest.php
+++ b/tests/PhpSpreadsheetTests/SpreadsheetTest.php
@@ -2,7 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheetTests;
 
-use PhpOffice\PhpSpreadsheet\Exception as ssException;
+use PhpOffice\PhpSpreadsheet\Exception;
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
 use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
 use PHPUnit\Framework\TestCase;
@@ -67,7 +67,7 @@ class SpreadsheetTest extends TestCase
     public function testAddSheetDuplicateTitle(): void
     {
         $spreadsheet = $this->getSpreadsheet();
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $sheet = new Worksheet();
         $sheet->setTitle('someSheet2');
         $spreadsheet->addSheet($sheet);
@@ -98,7 +98,7 @@ class SpreadsheetTest extends TestCase
     public function testRemoveSheetIndexTooHigh(): void
     {
         $spreadsheet = $this->getSpreadsheet();
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $spreadsheet->removeSheetByIndex(4);
     }
 
@@ -123,14 +123,14 @@ class SpreadsheetTest extends TestCase
     public function testGetSheetIndexTooHigh(): void
     {
         $spreadsheet = $this->getSpreadsheet();
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $spreadsheet->getSheet(4);
     }
 
     public function testGetIndexNonExistent(): void
     {
         $spreadsheet = $this->getSpreadsheet();
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $sheet = new Worksheet();
         $sheet->setTitle('someSheet4');
         $spreadsheet->getIndex($sheet);
@@ -175,14 +175,14 @@ class SpreadsheetTest extends TestCase
     public function testSetActiveSheetIndexTooHigh(): void
     {
         $spreadsheet = $this->getSpreadsheet();
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $spreadsheet->setActiveSheetIndex(4);
     }
 
     public function testSetActiveSheetNoSuchName(): void
     {
         $spreadsheet = $this->getSpreadsheet();
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $spreadsheet->setActiveSheetIndexByName('unknown');
     }
 
@@ -210,7 +210,7 @@ class SpreadsheetTest extends TestCase
 
     public function testAddExternalDuplicateName(): void
     {
-        $this->expectException(ssException::class);
+        $this->expectException(Exception::class);
         $spreadsheet = new Spreadsheet();
         $sheet = $spreadsheet->createSheet()->setTitle('someSheet1');
         $sheet->getCell('A1')->setValue(1);
@@ -275,4 +275,22 @@ class SpreadsheetTest extends TestCase
         self::assertEquals($countXfs + $index, $sheet3->getCell('A2')->getXfIndex());
         self::assertEquals($countXfs + $index, $sheet3->getRowDimension(2)->getXfIndex());
     }
+
+    public function testNotSerializable(): void
+    {
+        $this->spreadsheet = $spreadsheet = new Spreadsheet();
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('Spreadsheet objects cannot be serialized');
+        serialize($this->spreadsheet);
+    }
+
+    public function testNotJsonEncodable(): void
+    {
+        $this->spreadsheet = $spreadsheet = new Spreadsheet();
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('Spreadsheet objects cannot be json encoded');
+        json_encode($this->spreadsheet);
+    }
 }