diff --git a/block_int.h b/block_int.h
index f4bae04..6419513 100644
--- a/block_int.h
+++ b/block_int.h
@@ -55,6 +55,7 @@
 #define BLOCK_OPT_SUBFMT            "subformat"
 #define BLOCK_OPT_COMPAT_LEVEL      "compat"
 #define BLOCK_OPT_LAZY_REFCOUNTS    "lazy_refcounts"
+#define BLOCK_OPT_DEDUP             "dedup"
 
 typedef struct BdrvTrackedRequest BdrvTrackedRequest;