diff --git a/src/package.lisp b/src/package.lisp
index 4183f11b225516d7dd37886f57ee5c8bd726d896..6fda69c11f4abde251cff5d57d324cb983195323 100644
--- a/src/package.lisp
+++ b/src/package.lisp
@@ -20,6 +20,8 @@
 (defpackage :it.bese.fiveam
   (:use :common-lisp :alexandria)
   (:nicknames :5am :fiveam)
+  #+sb-package-locks
+  (:lock t)
   (:export
    ;; creating tests and test-suites
    #:make-suite