diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index d0c5ddeece..65e6b712a1 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -584,7 +584,7 @@ static void copy_schib_from_guest(SCHIB *dest, const SCHIB *src)
     }
 }
 
-int css_do_msch(SubchDev *sch, SCHIB *orig_schib)
+int css_do_msch(SubchDev *sch, const SCHIB *orig_schib)
 {
     SCSW *s = &sch->curr_status.scsw;
     PMCW *p = &sch->curr_status.pmcw;
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index a9ab587627..7180d68429 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -450,7 +450,7 @@ bool css_subch_visible(SubchDev *sch);
 void css_conditional_io_interrupt(SubchDev *sch);
 int css_do_stsch(SubchDev *sch, SCHIB *schib);
 bool css_schid_final(int m, uint8_t cssid, uint8_t ssid, uint16_t schid);
-int css_do_msch(SubchDev *sch, SCHIB *schib);
+int css_do_msch(SubchDev *sch, const SCHIB *schib);
 int css_do_xsch(SubchDev *sch);
 int css_do_csch(SubchDev *sch);
 int css_do_hsch(SubchDev *sch);