diff --git a/src/Cache/FilesystemCache.php b/src/Cache/FilesystemCache.php
index 34c5d0fdb..abb23580e 100644
--- a/src/Cache/FilesystemCache.php
+++ b/src/Cache/FilesystemCache.php
@@ -38,7 +38,7 @@ class FilesystemCache implements CacheInterface
 
     public function load(string $key): void
     {
-        if (file_exists($key)) {
+        if (is_file($key)) {
             @include_once $key;
         }
     }
@@ -78,7 +78,7 @@ class FilesystemCache implements CacheInterface
 
     public function getTimestamp(string $key): int
     {
-        if (!file_exists($key)) {
+        if (!is_file($key)) {
             return 0;
         }
 
diff --git a/src/ExtensionSet.php b/src/ExtensionSet.php
index 38b6ab8b9..50ddebfaf 100644
--- a/src/ExtensionSet.php
+++ b/src/ExtensionSet.php
@@ -103,7 +103,7 @@ final class ExtensionSet
 
         foreach ($this->extensions as $extension) {
             $r = new \ReflectionObject($extension);
-            if (file_exists($r->getFileName()) && ($extensionTime = filemtime($r->getFileName())) > $this->lastModified) {
+            if (is_file($r->getFileName()) && ($extensionTime = filemtime($r->getFileName())) > $this->lastModified) {
                 $this->lastModified = $extensionTime;
             }
         }