diff --git a/tools/putenv/putenv.php b/tools/putenv/putenv.php
index 37e50db..c74f404 100644
--- a/tools/putenv/putenv.php
+++ b/tools/putenv/putenv.php
@@ -61,7 +61,7 @@ class PutEnv {
             if (strlen($next) === 0 || $next[0] !== '=') {
                 continue;
             }
-            $this->content[$l] = $key . '=' . $value . PHP_EOF;
+            $this->content[$l] = $key . '=' . $value . \PHP_EOF;
             $changed++;
         }
         if ($changed === 0) {