diff --git a/src/Symfony/Component/HttpFoundation/CHANGELOG.md b/src/Symfony/Component/HttpFoundation/CHANGELOG.md
index 3f09854ac3221..945103371d5a4 100644
--- a/src/Symfony/Component/HttpFoundation/CHANGELOG.md
+++ b/src/Symfony/Component/HttpFoundation/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 6.4
 ---
 
+ * Add `Request::resetFormats()` internal method to reset the list of supported format to MIME type mappings
  * Make `HeaderBag::getDate()`, `Response::getDate()`, `getExpires()` and `getLastModified()` return a `DateTimeImmutable`
  * Support root-level `Generator` in `StreamedJsonResponse`
  * Add `UriSigner` from the HttpKernel component
diff --git a/src/Symfony/Component/HttpFoundation/Request.php b/src/Symfony/Component/HttpFoundation/Request.php
index 922014133293e..c7decbdf003de 100644
--- a/src/Symfony/Component/HttpFoundation/Request.php
+++ b/src/Symfony/Component/HttpFoundation/Request.php
@@ -1749,6 +1749,15 @@ public function preferSafeContent(): bool
         return $this->isSafeContentPreferred = AcceptHeader::fromString($this->headers->get('Prefer'))->has('safe');
     }
 
+    /**
+     * Resets the mappings of formats to mime types.
+     * @internal
+     */
+    public static function resetFormats(): void
+    {
+        static::initializeFormats();
+    }
+
     /*
      * The following methods are derived from code of the Zend Framework (1.10dev - 2010-01-24)
      *
diff --git a/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php b/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
index 7a4807ecf721e..06bedb287b2d0 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
@@ -33,6 +33,16 @@ protected function tearDown(): void
         Request::setTrustedHosts([]);
     }
 
+    public function testResetFormats()
+    {
+        $request = new Request();
+        $request->setFormat('json', ['application/problem+json']);
+        $modifiedRequestFormat = $request->getFormat('application/json');
+        $this->assertNull($modifiedRequestFormat);
+        Request::resetFormats();
+        $this->assertEquals('json', $request->getFormat('application/json'));
+    }
+
     public function testInitialize()
     {
         $request = new Request();
diff --git a/src/Symfony/Component/HttpKernel/CHANGELOG.md b/src/Symfony/Component/HttpKernel/CHANGELOG.md
index c1743b1d141b8..98886ce397ab6 100644
--- a/src/Symfony/Component/HttpKernel/CHANGELOG.md
+++ b/src/Symfony/Component/HttpKernel/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 6.4
 ---
 
+ * Add call to `Request::resetFormats()` in `Kernel::boot()` to reset the request formats at the start of a new main request.
  * Support backed enums in #[MapQueryParameter]
  * `BundleInterface` no longer extends `ContainerAwareInterface`
  * Add optional `$className` parameter to `ControllerEvent::getAttributes()`
diff --git a/src/Symfony/Component/HttpKernel/Kernel.php b/src/Symfony/Component/HttpKernel/Kernel.php
index 185c9686aa097..46dbdfd345018 100644
--- a/src/Symfony/Component/HttpKernel/Kernel.php
+++ b/src/Symfony/Component/HttpKernel/Kernel.php
@@ -110,6 +110,9 @@ public function boot()
     {
         if (true === $this->booted) {
             if (!$this->requestStackSize && $this->resetServices) {
+                if (method_exists(Request::class, 'resetFormats')) {
+                    Request::resetFormats();
+                }
                 if ($this->container->has('services_resetter')) {
                     $this->container->get('services_resetter')->reset();
                 }
diff --git a/src/Symfony/Component/HttpKernel/Tests/KernelTest.php b/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
index 94c498a0f2808..dfd829ed67b6d 100644
--- a/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/KernelTest.php
@@ -121,6 +121,34 @@ public function testInitializeContainerClearsOldContainers()
         $this->assertFileDoesNotExist($legacyContainerDir.'.legacy');
     }
 
+    public function testBootResetsRequestFormatsOnReset()
+    {
+        $request = new Request();
+        $request->setFormat('json', ['application/problem+json']);
+        $modifiedRequestFormat = $request->getFormat('application/json');
+
+        $httpKernelMock = $this->getMockBuilder(HttpKernel::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $httpKernelMock
+            ->expects($this->any())
+            ->method('handle')
+            ->with($request);
+
+        $kernel = $this->getKernel(['getHttpKernel']);
+        $kernel->expects($this->any())
+            ->method('getHttpKernel')
+            ->willReturn($httpKernelMock);
+
+        $kernel->handle($request);
+
+        $kernel->boot();
+        $kernel->handle($request);
+        $this->assertNull($modifiedRequestFormat);
+        $this->assertSame('json', $request->getFormat('application/json'));
+    }
+
     public function testBootInitializesBundlesAndContainer()
     {
         $kernel = $this->getKernel(['initializeBundles']);