diff --git a/src/danog/MadelineProto/Logger.php b/src/danog/MadelineProto/Logger.php
index 1a115b12..2af1bd40 100644
--- a/src/danog/MadelineProto/Logger.php
+++ b/src/danog/MadelineProto/Logger.php
@@ -126,7 +126,7 @@ class Logger
         self::$colors[self::ERROR] = implode(';', [self::foreground['white'], self::set['bold'], self::background['red']]);
         self::$colors[self::FATAL_ERROR] = implode(';', [self::foreground['red'], self::set['bold'], self::background['light_gray']]);
         try {
-            self::$isatty = defined('STDOUT') && posix_isatty(STDOUT);
+            self::$isatty = defined('STDOUT') && function_exists('posix_isatty') && posix_isatty(STDOUT);
         } catch (\danog\MadelineProto\Exception $e) {
         }
     }