diff --git a/BinaryFileResponse.php b/BinaryFileResponse.php
index 5bc8b0e16..a2b160f8a 100644
--- a/BinaryFileResponse.php
+++ b/BinaryFileResponse.php
@@ -126,7 +126,7 @@ public function setChunkSize(int $chunkSize): static
      */
     public function setAutoLastModified(): static
     {
-        $this->setLastModified(\DateTimeImmutable::createFromFormat('U', $this->file->getMTime()));
+        $this->setLastModified(\DateTimeImmutable::createFromFormat('U', $this->tempFileObject ? time() : $this->file->getMTime()));
 
         return $this;
     }
@@ -197,7 +197,9 @@ public function prepare(Request $request): static
         $this->offset = 0;
         $this->maxlen = -1;
 
-        if (false === $fileSize = $this->file->getSize()) {
+        if ($this->tempFileObject) {
+            $fileSize = $this->tempFileObject->fstat()['size'];
+        } elseif (false === $fileSize = $this->file->getSize()) {
             return $this;
         }
         $this->headers->remove('Transfer-Encoding');
diff --git a/Tests/BinaryFileResponseTest.php b/Tests/BinaryFileResponseTest.php
index b58276cf7..77bc32e8c 100644
--- a/Tests/BinaryFileResponseTest.php
+++ b/Tests/BinaryFileResponseTest.php
@@ -451,6 +451,9 @@ public function testCreateFromTemporaryFile()
         $this->assertEquals('attachment; filename=temp', $response->headers->get('Content-Disposition'));
 
         ob_start();
+        $response->setAutoLastModified();
+        $response->prepare(new Request());
+        $this->assertSame('7', $response->headers->get('Content-Length'));
         $response->sendContent();
         $string = ob_get_clean();
         $this->assertSame('foo,bar', $string);