diff --git a/target-i386/op.c b/target-i386/op.c
index 3f9afb17d3a98bf0a3bbe1e1ac1f33c9da674138..8b280070786dab88b0da46726e14e89f9a453419 100644
--- a/target-i386/op.c
+++ b/target-i386/op.c
@@ -980,8 +980,9 @@ void OPPROTO op_movl_drN_T0(void)
 
 void OPPROTO op_lmsw_T0(void)
 {
-    /* only 4 lower bits of CR0 are modified */
-    T0 = (env->cr[0] & ~0xf) | (T0 & 0xf);
+    /* only 4 lower bits of CR0 are modified. PE cannot be set to zero
+       if already set to one. */
+    T0 = (env->cr[0] & ~0xe) | (T0 & 0xf);
     helper_movl_crN_T0(0);
 }