diff --git a/core/genesis.go b/core/genesis.go
index 5c69b216c4..40d7996219 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -43,7 +43,7 @@ func WriteGenesisBlock(chainDb ethdb.Database, reader io.Reader) (*types.Block,
 	}
 
 	var genesis struct {
-		ChainConfig *ChainConfig
+		ChainConfig *ChainConfig `json:"config"`
 		Nonce       string
 		Timestamp   string
 		ParentHash  string