diff --git a/xen/include/xen/monitor.h b/xen/include/xen/monitor.h
index 6b17a93071..713d54f7c1 100644
--- a/xen/include/xen/monitor.h
+++ b/xen/include/xen/monitor.h
@@ -27,7 +27,7 @@
 struct domain;
 struct xen_domctl_monitor_op;
 
-int monitor_domctl(struct domain *d, struct xen_domctl_monitor_op *op);
+int monitor_domctl(struct domain *d, struct xen_domctl_monitor_op *mop);
 void monitor_guest_request(void);
 
 int monitor_traps(struct vcpu *v, bool sync, vm_event_request_t *req);