diff --git a/migrations/7_pol_migration.js b/migrations/7_pol_migration.js
index a30ca7c5..fa373835 100644
--- a/migrations/7_pol_migration.js
+++ b/migrations/7_pol_migration.js
@@ -93,7 +93,7 @@ module.exports = async function(deployer, _, _) {
     const maticAmountToMintAndMigrateInDepositManager = oneEther.mul(web3.utils.toBN('1000000000')).toString() // 100 ethers
     await migrateMatic(governance, newDepositManager, maticAmountToMintAndMigrateInDepositManager)
 
-    const newDepositManagerPOLBalance = await polToken.methods.balanceOf(newDepositManager.address).call()
+    const newDepositManagerPOLBalance = await polToken.contract.methods.balanceOf(newDepositManager.address).call()
     utils.assertBigNumberEquality(newDepositManagerPOLBalance, maticAmountToMintAndMigrateInDepositManager)
 
     // Update contract addresses.
diff --git a/migrations/utils.js b/migrations/utils.js
index f369a836..0100c094 100644
--- a/migrations/utils.js
+++ b/migrations/utils.js
@@ -18,3 +18,12 @@ export async function updateContractMap(governance, registry, name, value) {
     registry.contract.methods.updateContractMap(ethUtils.keccak256(name), value).encodeABI()
   )
 }
+
+export function assertBigNumberEquality(num1, num2) {
+  if (!ethUtils.BN.isBN(num1)) num1 = web3.utils.toBN(num1.toString())
+  if (!ethUtils.BN.isBN(num2)) num2 = web3.utils.toBN(num2.toString())
+  assert(
+    num1.eq(num2),
+    `expected ${num1.toString(10)} and ${num2.toString(10)} to be equal`
+  )
+}