symfony
diff --git a/‎src/Symfony/Component/HttpKernel/HttpCache/ResponseCacheStrategy.php‎
Lines changed: 7 additions & 10 deletions b/‎src/Symfony/Component/HttpKernel/HttpCache/ResponseCacheStrategy.php‎
Lines changed: 7 additions & 10 deletions
@@ -37,8 +37,8 @@ class ResponseCacheStrategy implements ResponseCacheStrategyInterface
     private int $embeddedResponses = 0;
     private bool $isNotCacheableResponseEmbedded = false;
     private int $age = 0;
-    private array $lastModified = null;
-    private $flagDirectives = [
+    private \DateTimeInterface|null|false $lastModified = null;
+    private array $flagDirectives = [
         'no-cache' => null,
         'no-store' => null,
         'no-transform' => null,
@@ -92,8 +92,8 @@ public function add(Response $response)
         $expires = null !== $expires ? (int) $expires->format('U') - (int) $response->getDate()->format('U') : null;
         $this->storeRelativeAgeDirective('expires', $expires >= 0 ? $expires : null, 0, $isHeuristicallyCacheable);
 
-        $lastModified = $response->getLastModified();
         if (false !== $this->lastModified) {
+            $lastModified = $response->getLastModified();
             $this->lastModified = $lastModified ? max($this->lastModified, $lastModified) : false;
         }
     }
@@ -116,7 +116,7 @@ public function update(Response $response)
         $response->headers->set('Age', $this->age);
 
         if ($this->isNotCacheableResponseEmbedded) {
-            $response->setLastModified(null);
+            $response->setLastModified();
 
             if ($this->flagDirectives['no-store']) {
                 $response->headers->set('Cache-Control', 'no-cache, no-store, must-revalidate');
@@ -169,17 +169,14 @@ private function willMakeFinalResponseUncacheable(Response $response): bool
         // RFC2616: A response received with a status code of 200, 203, 300, 301 or 410
         // MAY be stored by a cache […] unless a cache-control directive prohibits caching.
         if ($response->headers->hasCacheControlDirective('no-cache')
-            || $response->headers->getCacheControlDirective('no-store')
+            || $response->headers->hasCacheControlDirective('no-store')
         ) {
             return true;
         }
 
-        // Last-Modified and Etag headers cannot be merged, they render the response uncacheable
+        // Etag headers cannot be merged, they render the response uncacheable
         // by default (except if the response also has max-age etc.).
-        if (\in_array($response->getStatusCode(), [200, 203, 300, 301, 410])
-            && null === $response->getLastModified()
-            && null === $response->getEtag()
-        ) {
+        if (null === $response->getEtag() && \in_array($response->getStatusCode(), [200, 203, 300, 301, 410])) {
             return false;
         }