diff --git a/blkmaker.h b/blkmaker.h
index 70a3c86..9759da2 100644
--- a/blkmaker.h
+++ b/blkmaker.h
@@ -12,7 +12,7 @@ extern "C" {
 #endif
 
 #define BLKMAKER_VERSION (6L)
-#define BLKMAKER_MAX_BLOCK_VERSION (3)
+#define BLKMAKER_MAX_BLOCK_VERSION (4)
 
 extern bool (*blkmk_sha256_impl)(void *hash_out, const void *data, size_t datasz);