diff --git a/vl.h b/vl.h
index 2f69899..119769b 100644
--- a/vl.h
+++ b/vl.h
@@ -360,6 +360,7 @@
 extern BlockDriver bdrv_qcow;
 extern BlockDriver bdrv_vmdk;
 extern BlockDriver bdrv_cloop;
+extern BlockDriver bdrv_dmg;
 
 void bdrv_init(void);
 BlockDriver *bdrv_find_format(const char *format_name);