diff --git a/clash.asd b/clash.asd
old mode 100644
new mode 100755
index cd78c11..66d2ff3
--- a/clash.asd
+++ b/clash.asd
@@ -30,7 +30,7 @@
                                    (:file "sbcl-locking" :depends-on ("package"))
                                    #+cmu
                                    (:file "cmu-locking" :depends-on ("package"))
-                                   #+lispworks4.1
+                                   #+lispworks
                                    (:file "lwl-locking" :depends-on ("package"))
                                    #+allegro
                                    (:file "acl-locking" :depends-on ("package"))))
@@ -88,7 +88,7 @@
                                    (:file "simple-sbcl")
                                    #+cmu
                                    (:file "simple-cmu")
-                                   #+lispworks4.1
+                                   #+lispworks
                                    (:file "simple-lwl")
                                    #+allegro
                                    (:file "simple-acl"))
diff --git a/src/lwl-locking.lisp b/src/lwl-locking.lisp
old mode 100644
new mode 100755
index ddf61c0..f6e08f2
--- a/src/lwl-locking.lisp
+++ b/src/lwl-locking.lisp
@@ -15,9 +15,7 @@
 ;;; Locking primitives for LWL
 
 (defmacro pop-atomically (place)
-  `(mp:without-preemption
-    (pop ,place)))
+  `(system:atomic-pop ,place))
 
 (defmacro push-atomically (value place)
-  `(mp:without-preemption
-    (push ,value ,place)))
+  `(system:atomic-push ,value ,place))