diff --git a/src/bin/install-wp-tests.sh b/src/bin/install-wp-tests.sh
index 1ab2d39c..6373744b 100755
--- a/src/bin/install-wp-tests.sh
+++ b/src/bin/install-wp-tests.sh
@@ -4,6 +4,7 @@ set -ex
 WP_VERSION=$1
 WC_VERSION=$2
 
+TMPDIR="/tmp"
 WP_TESTS_DIR="/tmp/wordpress-tests-lib"
 WP_CORE_DIR="/tmp/wordpress"