diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h
index ded29e7494..5474293c4f 100644
--- a/include/block/block_int-io.h
+++ b/include/block/block_int-io.h
@@ -65,7 +65,7 @@ static inline int coroutine_fn bdrv_co_pread(BdrvChild *child,
 }
 
 static inline int coroutine_fn bdrv_co_pwrite(BdrvChild *child,
-    int64_t offset, unsigned int bytes, void *buf, BdrvRequestFlags flags)
+    int64_t offset, unsigned int bytes, const void *buf, BdrvRequestFlags flags)
 {
     QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
     IO_CODE();