diff --git a/composer.json b/composer.json
index 088875e..8a496b4 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
     "require": {
         "php": ">=7.0",
         "google/cloud-storage": "^1.3",
-        "league/flysystem": "^1.0"
+        "league/flysystem": "^1.0.40"
     },
     "require-dev": {
         "phpunit/phpunit": "~5.0|~6.0"