diff --git a/Filesystem.php b/Filesystem.php
index d2131c9b9d..eb14fee9e9 100644
--- a/Filesystem.php
+++ b/Filesystem.php
@@ -44,7 +44,7 @@ public function copy(string $originFile, string $targetFile, bool $overwriteNewe
         $this->mkdir(\dirname($targetFile));
 
         $doCopy = true;
-        if (!$overwriteNewerFiles && null === parse_url($originFile, PHP_URL_HOST) && is_file($targetFile)) {
+        if (!$overwriteNewerFiles && null === parse_url($originFile, \PHP_URL_HOST) && is_file($targetFile)) {
             $doCopy = filemtime($originFile) > filemtime($targetFile);
         }
 
@@ -114,7 +114,7 @@ public function mkdir($dirs, int $mode = 0777)
      */
     public function exists($files)
     {
-        $maxPathLength = PHP_MAXPATHLEN - 2;
+        $maxPathLength = \PHP_MAXPATHLEN - 2;
 
         foreach ($this->toIterable($files) as $file) {
             if (\strlen($file) > $maxPathLength) {
@@ -289,7 +289,7 @@ public function rename(string $origin, string $target, bool $overwrite = false)
      */
     private function isReadable(string $filename): bool
     {
-        $maxPathLength = PHP_MAXPATHLEN - 2;
+        $maxPathLength = \PHP_MAXPATHLEN - 2;
 
         if (\strlen($filename) > $maxPathLength) {
             throw new IOException(sprintf('Could not check if file is readable because path length exceeds %d characters.', $maxPathLength), 0, null, $filename);
@@ -574,7 +574,7 @@ public function isAbsolutePath(string $file)
                 && ':' === $file[1]
                 && strspn($file, '/\\', 2, 1)
             )
-            || null !== parse_url($file, PHP_URL_SCHEME)
+            || null !== parse_url($file, \PHP_URL_SCHEME)
         ;
     }
 
@@ -690,7 +690,7 @@ public function appendToFile(string $filename, $content)
             throw new IOException(sprintf('Unable to write to the "%s" directory.', $dir), 0, null, $dir);
         }
 
-        if (false === @file_put_contents($filename, $content, FILE_APPEND)) {
+        if (false === @file_put_contents($filename, $content, \FILE_APPEND)) {
             throw new IOException(sprintf('Failed to write file "%s".', $filename), 0, null, $filename);
         }
     }
diff --git a/Tests/FilesystemTest.php b/Tests/FilesystemTest.php
index c6e63fbc56..dcd6a393a9 100644
--- a/Tests/FilesystemTest.php
+++ b/Tests/FilesystemTest.php
@@ -377,7 +377,7 @@ public function testFilesExistsFails()
             $this->markTestSkipped('Long file names are an issue on Windows');
         }
         $basePath = $this->workspace.'\\directory\\';
-        $maxPathLength = PHP_MAXPATHLEN - 2;
+        $maxPathLength = \PHP_MAXPATHLEN - 2;
 
         $oldPath = getcwd();
         mkdir($basePath);
diff --git a/Tests/FilesystemTestCase.php b/Tests/FilesystemTestCase.php
index 396a3ab2e8..76cfb9f9ff 100644
--- a/Tests/FilesystemTestCase.php
+++ b/Tests/FilesystemTestCase.php
@@ -159,7 +159,7 @@ protected function markAsSkippedIfSymlinkIsMissing($relative = false)
         }
 
         // https://bugs.php.net/69473
-        if ($relative && '\\' === \DIRECTORY_SEPARATOR && 1 === PHP_ZTS) {
+        if ($relative && '\\' === \DIRECTORY_SEPARATOR && 1 === \PHP_ZTS) {
             $this->markTestSkipped('symlink does not support relative paths on thread safe Windows PHP versions');
         }
     }