Cast arguments for new Bignumbers() to string.

ui/app/conversion-util.js

@@ -46,7 +46,7 @@ const decToBigNumberViaString = n => R.pipe(String, toBigNumber['dec'])
 // Setter Maps
 const toBigNumber = {
   hex: n => new BigNumber(stripHexPrefix(n), 16),
-  dec: n => new BigNumber(n, 10),
+  dec: n => new BigNumber(String(n), 10),
   BN: n => new BigNumber(n.toString(16), 16),
 }
 const toNormalizedDenomination = {
@@ -154,7 +154,7 @@ const subtractCurrencies = (a, b, options = {}) => {
     bBase,
     ...conversionOptions
   } = options
-  const value = (new BigNumber(a, aBase)).minus(b, bBase)
+  const value = (new BigNumber(String(a), aBase)).minus(b, bBase)
 
   return converter({
     value,

ui/app/helpers/confirm-transaction/util.js

@@ -141,7 +141,7 @@ export function hasUnconfirmedTransactions (state) {
 
 export function roundExponential (value) {
   const PRECISION = 4
-  const bigNumberValue = new BigNumber(value)
+  const bigNumberValue = new BigNumber(String(value))
 
   // In JS, numbers with exponentials greater than 20 get displayed as an exponential.
   return bigNumberValue.e > 20 ? Number(bigNumberValue.toPrecision(PRECISION)) : value

ui/app/token-util.js

@@ -44,7 +44,7 @@ async function getSymbolAndDecimals (tokenAddress, existingTokens = []) {
 
 function calcTokenAmount (value, decimals) {
   const multiplier = Math.pow(10, Number(decimals || 0))
-  return new BigNumber(value).div(multiplier).toNumber()
+  return new BigNumber(String(value)).div(multiplier).toNumber()
 }