diff --git a/Cargo.toml b/Cargo.toml
index 913b4c5f2..f52f0dc85 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -66,6 +66,7 @@ json-tests = ["ethcore/json-tests"]
 stratum = ["ipc"]
 ethkey-cli = ["ethcore/ethkey-cli"]
 ethstore-cli = ["ethcore/ethstore-cli"]
+evm-debug = ["ethcore/evm-debug"]
 
 [[bin]]
 path = "parity/main.rs"
diff --git a/ethcore/src/evm/evm.rs b/ethcore/src/evm/evm.rs
index 813819250..8d2202480 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 {
+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
diff --git a/ethcore/src/evm/interpreter/mod.rs b/ethcore/src/evm/interpreter/mod.rs
index d1b9b18bc..e95fb943e 100644
--- a/ethcore/src/evm/interpreter/mod.rs
+++ b/ethcore/src/evm/interpreter/mod.rs
@@ -126,7 +126,7 @@ impl<Cost: CostType> evm::Evm for Interpreter<Cost> {
 			gasometer.current_gas = gasometer.current_gas - gas_cost;
 
 			evm_debug!({
-				println!("[0x{:x}][{}(0x{:x}) Gas: {:x}\n  Gas Before: {:x}",
+				println!("[0x{:x}][{}(0x{:x}) Gas: {:?}\n  Gas Before: {:?}",
 					reader.position,
 					color(instruction, info.name),
 					instruction,