diff --git a/ethcore/src/evm/evm.rs b/ethcore/src/evm/evm.rs
index 68056a0b9..f399f57bb 100644
--- a/ethcore/src/evm/evm.rs
+++ b/ethcore/src/evm/evm.rs
@@ -113,7 +113,10 @@ impl<'a> Finalize for Result<GasLeft<'a>> {
 }
 
 /// Cost calculation type. For low-gas usage we calculate costs using usize instead of U256
-pub trait CostType: ops::Mul<Output=Self> + ops::Div<Output=Self> + ops::Add<Output=Self> + ops::Sub<Output=Self> + ops::Shr<usize, Output=Self> + ops::Shl<usize, Output=Self> + cmp::Ord + Sized + From<usize> + Copy + fmt::Debug {
+pub trait CostType: Sized : From<usize> + Copy
+	+ ops::Mul<Output=Self> + ops::Div<Output=Self> + ops::Add<Output=Self> +ops::Sub<Output=Self>
+	+ ops::Shr<usize, Output=Self> + ops::Shl<usize, Output=Self>
+	+ cmp::Ord + fmt::Debug {
 	/// Converts this cost into `U256`
 	fn as_u256(&self) -> U256;
 	/// Tries to fit `U256` into this `Cost` type