diff --git a/currencies/src/mock.rs b/currencies/src/mock.rs
index 97f3b40c1..621876964 100644
--- a/currencies/src/mock.rs
+++ b/currencies/src/mock.rs
@@ -62,7 +62,7 @@ impl pallet_balances::Config for Runtime {
 }
 
 parameter_type_with_key! {
-	pub ExistentialDeposits: |currency_id: CurrencyId| -> Balance {
+	pub ExistentialDeposits: |_currency_id: CurrencyId| -> Balance {
 		Default::default()
 	};
 }
diff --git a/traits/src/lib.rs b/traits/src/lib.rs
index 288390795..d8dfbab39 100644
--- a/traits/src/lib.rs
+++ b/traits/src/lib.rs
@@ -68,3 +68,7 @@ pub struct TimestampedValue<Value: Ord + PartialOrd, Moment> {
 pub trait Happened<T> {
 	fn happened(t: &T);
 }
+
+pub trait Contains<T> {
+	fn contains(t: &T) -> bool;
+}