diff --git a/ethcore/builtin/src/lib.rs b/ethcore/builtin/src/lib.rs
index 71504aee4ae..a3c50c3c381 100644
--- a/ethcore/builtin/src/lib.rs
+++ b/ethcore/builtin/src/lib.rs
@@ -218,8 +218,8 @@ impl Builtin {
 impl From<ethjson::spec::Builtin> for Builtin {
 	fn from(b: ethjson::spec::Builtin) -> Self {
 		let pricer: Box<dyn Pricer> = match b.pricing {
-			ethjson::spec::Pricing::Blake2F(cost_per_round) => {
-				Box::new(cost_per_round)
+			ethjson::spec::Pricing::Blake2F { gas_per_round } => {
+				Box::new(gas_per_round)
 			},
 			ethjson::spec::Pricing::Linear(linear) => {
 				Box::new(Linear {
diff --git a/json/src/spec/builtin.rs b/json/src/spec/builtin.rs
index 20ebbc3c636..c4f9f4e1ec8 100644
--- a/json/src/spec/builtin.rs
+++ b/json/src/spec/builtin.rs
@@ -18,8 +18,6 @@
 
 use uint::Uint;
 
-/// Price per round of Blake2 compression.
-pub type Blake2F = u64;
 
 /// Linear pricing.
 #[derive(Debug, PartialEq, Deserialize, Clone)]
@@ -69,7 +67,10 @@ pub struct AltBn128Pairing {
 #[serde(rename_all = "snake_case")]
 pub enum Pricing {
 	/// Pricing for Blake2 compression function: each call costs the same amount per round.
-	Blake2F(Blake2F),
+	Blake2F {
+		/// Price per round of Blake2 compression function.
+		gas_per_round: u64,
+	},
 	/// Linear pricing.
 	Linear(Linear),
 	/// Pricing for modular exponentiation.
@@ -117,11 +118,11 @@ mod tests {
 		let s = r#"{
 			"name": "blake2_f",
 			"activate_at": "0xffffff",
-			"pricing": { "blake2_f": 123 }
+			"pricing": { "blake2_f": { "gas_per_round": 123 } }
 		}"#;
 		let deserialized: Builtin = serde_json::from_str(s).unwrap();
 		assert_eq!(deserialized.name, "blake2_f");
-		assert_eq!(deserialized.pricing, Pricing::Blake2F(123));
+		assert_eq!(deserialized.pricing, Pricing::Blake2F { gas_per_round: 123 });
 		assert!(deserialized.activate_at.is_some());
 	}