diff --git a/src/Symfony/Component/HttpFoundation/JsonResponse.php b/src/Symfony/Component/HttpFoundation/JsonResponse.php
index f6b247bfa1..79791a7233 100644
--- a/src/Symfony/Component/HttpFoundation/JsonResponse.php
+++ b/src/Symfony/Component/HttpFoundation/JsonResponse.php
@@ -43,6 +43,10 @@ class JsonResponse extends Response
     {
         parent::__construct('', $status, $headers);
 
+        if ($json && !\is_string($data) && !is_numeric($data) && !\is_callable([$data, '__toString'])) {
+            throw new \TypeError(sprintf('"%s": If $json is set to true, argument $data must be a string or object implementing __toString(), "%s" given.', __METHOD__, get_debug_type($data)));
+        }
+
         if (null === $data) {
             $data = new \ArrayObject();
         }
@@ -77,13 +81,13 @@ class JsonResponse extends Response
      *     return JsonResponse::fromJsonString('{"key": "value"}')
      *         ->setSharedMaxAge(300);
      *
-     * @param string|null $data    The JSON response string
-     * @param int         $status  The response status code
-     * @param array       $headers An array of response headers
+     * @param string $data    The JSON response string
+     * @param int    $status  The response status code
+     * @param array  $headers An array of response headers
      *
      * @return static
      */
-    public static function fromJsonString($data = null, $status = 200, $headers = [])
+    public static function fromJsonString($data, $status = 200, $headers = [])
     {
         return new static($data, $status, $headers, true);
     }
diff --git a/src/Symfony/Component/HttpFoundation/Tests/JsonResponseTest.php b/src/Symfony/Component/HttpFoundation/Tests/JsonResponseTest.php
index 0468ebd594..8c37fd771b 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/JsonResponseTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/JsonResponseTest.php
@@ -240,6 +240,44 @@ class JsonResponseTest extends TestCase
 
         $this->assertEquals('/**/ಠ_ಠ["foo"].bar[0]({"foo":"bar"});', $response->getContent());
     }
+
+    public function testConstructorWithNullAsDataThrowsAnUnexpectedValueException()
+    {
+        $this->expectException(\TypeError::class);
+        $this->expectExceptionMessage('If $json is set to true, argument $data must be a string or object implementing __toString(), "null" given.');
+
+        new JsonResponse(null, 200, [], true);
+    }
+
+    public function testfromJsonStringConstructorWithNullAsDataThrowsAnUnexpectedValueException()
+    {
+        $this->expectException(\TypeError::class);
+        $this->expectExceptionMessage('If $json is set to true, argument $data must be a string or object implementing __toString(), "null" given.');
+
+        JsonResponse::fromJsonString(null);
+    }
+
+    public function testConstructorWithObjectWithToStringMethod()
+    {
+        $class = new class() {
+            public function __toString()
+            {
+                return '{}';
+            }
+        };
+
+        $response = new JsonResponse($class, 200, [], true);
+
+        $this->assertSame('{}', $response->getContent());
+    }
+
+    public function testConstructorWithObjectWithoutToStringMethodThrowsAnException()
+    {
+        $this->expectException(\TypeError::class);
+        $this->expectExceptionMessage('If $json is set to true, argument $data must be a string or object implementing __toString(), "stdClass" given.');
+
+        new JsonResponse(new \stdClass(), 200, [], true);
+    }
 }
 
 if (interface_exists('JsonSerializable', false)) {
diff --git a/src/Symfony/Component/HttpFoundation/composer.json b/src/Symfony/Component/HttpFoundation/composer.json
index 79f4b396d0..7b3a692bd6 100644
--- a/src/Symfony/Component/HttpFoundation/composer.json
+++ b/src/Symfony/Component/HttpFoundation/composer.json
@@ -18,7 +18,8 @@
     "require": {
         "php": ">=7.1.3",
         "symfony/mime": "^4.3|^5.0",
-        "symfony/polyfill-mbstring": "~1.1"
+        "symfony/polyfill-mbstring": "~1.1",
+        "symfony/polyfill-php80": "^1.15"
     },
     "require-dev": {
         "predis/predis": "~1.0",