--- a/pallets/nonfungible/src/lib.rs
+++ b/pallets/nonfungible/src/lib.rs
@@ -177,18 +177,18 @@
 			.checked_add(1)
 			.ok_or(ArithmeticError::Overflow)?;
 
-		let balance = <AccountBalance<T>>::get((collection.id, sender))
+		let balance = <AccountBalance<T>>::get((collection.id, token_data.owner.clone()))
 			.checked_sub(1)
 			.ok_or(ArithmeticError::Overflow)?;
 
 		if balance == 0 {
-			<AccountBalance<T>>::remove((collection.id, sender));
+			<AccountBalance<T>>::remove((collection.id, token_data.owner.clone()));
 		} else {
-			<AccountBalance<T>>::insert((collection.id, sender), balance);
+			<AccountBalance<T>>::insert((collection.id, token_data.owner.clone()), balance);
 		}
 		// =========
 
-		<Owned<T>>::remove((collection.id, &token_data.owner, token));
+		<Owned<T>>::remove((collection.id, &token_data.owner.clone(), token));
 		<TokensBurnt<T>>::insert(collection.id, burnt);
 		<TokenData<T>>::remove((collection.id, token));
 		let old_spender = <Allowance<T>>::take((collection.id, token));
--- a/tests/src/approve.test.ts
+++ b/tests/src/approve.test.ts
@@ -24,7 +24,6 @@
 } from './util/helpers';
 
 chai.use(chaiAsPromised);
-const expect = chai.expect;
 
 describe('Integration Test approve(spender, collection_id, item_id, amount):', () => {
   let alice: IKeyringPair;
--- a/tests/src/inflation.test.ts
+++ b/tests/src/inflation.test.ts
@@ -18,16 +18,16 @@
       const totalIssuanceStart = (await api.query.inflation.startingYearTotalIssuance()).toBigInt();
       const blockInflation = (await api.query.inflation.blockInflation()).toBigInt();
 
-      const YEAR = 5259600n; // Blocks in one year
+      // const YEAR = 5259600n;  // 6-second block. Blocks in one year
+      const YEAR = 2629800n; // 12-second block. Blocks in one year
+
       const totalExpectedInflation = totalIssuanceStart / 10n;
       const totalActualInflation = blockInflation * YEAR / blockInterval;
 
       const tolerance = 0.00001; // Relative difference per year between theoretical and actual inflation
-      let abs = totalExpectedInflation / totalActualInflation - 1n;
-      if (abs < 0n) {
-        abs = -abs;
-      }
-      expect(abs <= tolerance).to.be.true;
+      const expectedInflation = totalExpectedInflation / totalActualInflation - 1n;
+
+      expect(Math.abs(Number(expectedInflation))).to.be.lessThanOrEqual(tolerance);
     });
   });