diff --git a/composer.json b/composer.json
index 1004aa2042..fa06d7cd29 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
         "drupal/coder": "^8.3.2",
         "jcalderonzumba/gastonjs": "^1.0.2",
         "jcalderonzumba/mink-phantomjs-driver": "^0.3.1",
-        "mikey179/vfsstream": "^1.2 || 2.0.x-dev",
+        "mikey179/vfsstream": "^1.2 || v1.x-dev",
         "phpunit/phpunit": "^6.5 || ^7",
         "phpspec/prophecy": "^1.7",
         "symfony/css-selector": "^3.4.0",
diff --git a/core/drupalci.yml b/core/drupalci.yml
index 3a399d4ba3..b3d29ff951 100644
--- a/core/drupalci.yml
+++ b/core/drupalci.yml
@@ -18,7 +18,7 @@ build:
       # Update PHPUnit & friends.
       container_command:
         commands:
-          - "sudo -u www-data /usr/local/bin/composer require composer/composer:dev-master mikey179/vfsstream:2.0.x-dev --no-progress"
+          - "sudo -u www-data /usr/local/bin/composer require composer/composer:dev-master mikey179/vfsstream:v1.x-dev --no-progress"
           - "sudo -u www-data /usr/local/bin/composer update typo3/phar-stream-wrapper pear/archive_tar --with-dependencies --no-progress"
       # run_tests task is executed several times in order of performance speeds.
       # halt-on-fail can be set on the run_tests tasks in order to fail fast.