diff --git a/include/exec/memory.h b/include/exec/memory.h
index 1be58f6..2bf5e23 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1852,7 +1852,7 @@
  *         range.
  */
 void memory_region_notify_iommu_one(IOMMUNotifier *notifier,
-                                    IOMMUTLBEvent *event);
+                                    const IOMMUTLBEvent *event);
 
 /**
  * memory_region_unmap_iommu_notifier_range: notify a unmap for an IOMMU
diff --git a/system/memory.c b/system/memory.c
index 74cd73e..f3a37c9 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -2006,9 +2006,9 @@
 }
 
 void memory_region_notify_iommu_one(IOMMUNotifier *notifier,
-                                    IOMMUTLBEvent *event)
+                                    const IOMMUTLBEvent *event)
 {
-    IOMMUTLBEntry *entry = &event->entry;
+    const IOMMUTLBEntry *entry = &event->entry;
     hwaddr entry_end = entry->iova + entry->addr_mask;
     IOMMUTLBEntry tmp = *entry;