diff --git a/docs/spec/blockchain/blockchain.md b/docs/spec/blockchain/blockchain.md
index 73a24f649..ca64add52 100644
--- a/docs/spec/blockchain/blockchain.md
+++ b/docs/spec/blockchain/blockchain.md
@@ -115,10 +115,10 @@ height and round by a sufficient set of validators.
 
 ```go
 type Commit struct {
+    HeightNum  int64
+    RoundNum   int
 	BlockID    BlockID
 	Precommits []*CommitSig
-	RoundNum   int
-	HeightNum  int64
 }
 ```