2 files changed, 9 insertions, 5 deletions
diff --git a/app/scripts/controllers/preferences.js b/app/scripts/controllers/preferences.js
index bc4848421..c42f47037 100644
--- a/app/scripts/controllers/preferences.js
+++ b/app/scripts/controllers/preferences.js
@@ -26,23 +26,23 @@ class PreferencesController {
     return this.store.getState().selectedAddress
   }
 
-  addToken (rawAddress, symbol, decimals) {
+  async addToken (rawAddress, symbol, decimals) {
     const address = normalizeAddress(rawAddress)
     const newEntry = { address, symbol, decimals }
 
     const tokens = this.store.getState().tokens
-    const previousIndex = tokens.find((token, index) => {
+    const previousEntry = tokens.find((token, index) => {
       return token.address === address
     })
+    const previousIndex = tokens.indexOf(previousEntry)
 
-    if (previousIndex) {
+    if (previousEntry) {
       tokens[previousIndex] = newEntry
     } else {
       tokens.push(newEntry)
     }
 
     this.store.updateState({ tokens })
-    return Promise.resolve()
   }
 
   getTokens () {
diff --git a/app/scripts/lib/tx-gas-utils.js b/app/scripts/lib/tx-gas-utils.js
index 7e72ea71d..56bee19f7 100644
--- a/app/scripts/lib/tx-gas-utils.js
+++ b/app/scripts/lib/tx-gas-utils.js
@@ -22,7 +22,11 @@ module.exports = class txProvideUtil {
     try {
       estimatedGasHex = await this.estimateTxGas(txMeta, block.gasLimit)
     } catch (err) {
-      if (err.message.includes('Transaction execution error.')) {
+      const simulationFailed = (
+        err.message.includes('Transaction execution error.') ||
+        err.message.includes('gas required exceeds allowance or always failing transaction')
+      )
+      if ( simulationFailed ) {
         txMeta.simulationFails = true
         return txMeta
       }