diff --git a/src/bridge/BridgeSyncContext.js b/src/bridge/BridgeSyncContext.js
index c469e20a..08b94f50 100644
--- a/src/bridge/BridgeSyncContext.js
+++ b/src/bridge/BridgeSyncContext.js
@@ -15,7 +15,7 @@ import { setAccountSyncState } from 'actions/bridgeSync'
 import { bridgeSyncSelector, syncStateLocalSelector } from 'reducers/bridgeSync'
 import type { BridgeSyncState } from 'reducers/bridgeSync'
 import { accountsSelector } from 'reducers/accounts'
-import { SYNC_BOOT_DELAY, SYNC_ALL_INTERVAL } from 'config/constants'
+import { SYNC_BOOT_DELAY, SYNC_ALL_INTERVAL, SYNC_MAX_CONCURRENT } from 'config/constants'
 import { getBridgeForCurrency } from '.'
 
 type BridgeSyncProviderProps = {
@@ -87,7 +87,7 @@ class Provider extends Component<BridgeSyncProviderOwnProps, Sync> {
       })
     }
 
-    const syncQueue = priorityQueue(synchronize, 2)
+    const syncQueue = priorityQueue(synchronize, SYNC_MAX_CONCURRENT)
 
     let skipUnderPriority: number = -1
 
diff --git a/src/bridge/LibcoreBridge.js b/src/bridge/LibcoreBridge.js
index ffe8f8b5..9823a762 100644
--- a/src/bridge/LibcoreBridge.js
+++ b/src/bridge/LibcoreBridge.js
@@ -1,5 +1,4 @@
 // @flow
-import logger from 'logger'
 import React from 'react'
 import { Observable } from 'rxjs'
 import { map } from 'rxjs/operators'
@@ -101,7 +100,7 @@ const LibcoreBridge: WalletBridge<Transaction> = {
       })()
       return {
         unsubscribe() {
-          logger.warn('LibcoreBridge: unsub sync not implemented')
+          // LibcoreBridge: unsub sync not currently implemented
         },
       }
     }),
diff --git a/src/config/constants.js b/src/config/constants.js
index 90be4ff9..5b69bf85 100644
--- a/src/config/constants.js
+++ b/src/config/constants.js
@@ -1,12 +1,20 @@
 // @flow
 
+const intFromEnv = (key: string, def: number) => {
+  const v = process.env[key]
+  if (!isNaN(v)) return parseInt(v, 10)
+  return def
+}
+
+export const SYNC_MAX_CONCURRENT = intFromEnv('LEDGER_SYNC_MAX_CONCURRENT', 2)
 export const SYNC_BOOT_DELAY = 2 * 1000
 export const SYNC_ALL_INTERVAL = 60 * 1000
+
 export const CHECK_APP_INTERVAL_WHEN_INVALID = 600
 export const CHECK_APP_INTERVAL_WHEN_VALID = 1200
 export const CHECK_UPDATE_DELAY = 5e3
 
-export const DEVICE_DISCONNECT_DEBOUNCE = 1000
+export const DEVICE_DISCONNECT_DEBOUNCE = intFromEnv('LEDGER_DEVICE_DISCONNECT_DEBOUNCE', 1000)
 
 export const MODAL_ADD_ACCOUNT = 'MODAL_ADD_ACCOUNT'
 export const MODAL_OPERATION_DETAILS = 'MODAL_OPERATION_DETAILS'
diff --git a/src/helpers/withLibcore.js b/src/helpers/withLibcore.js
index 37a9c49d..a2c966a5 100644
--- a/src/helpers/withLibcore.js
+++ b/src/helpers/withLibcore.js
@@ -1,12 +1,10 @@
 // @flow
 
 import invariant from 'invariant'
-import logger from 'logger'
 
 const core = require('@ledgerhq/ledger-core')
 
 let walletPoolInstance: ?Object = null
-let queue = Promise.resolve()
 
 // TODO: `core` and `NJSWalletPool` should be typed
 type Job<A> = (Object, Object) => Promise<A>
@@ -21,11 +19,5 @@ export default function withLibcore<A>(job: Job<A>): Promise<A> {
   const walletPool = walletPoolInstance
   invariant(walletPool, 'core.instanciateWalletPool returned null !!')
 
-  const p = queue.then(() => job(core, walletPool))
-
-  queue = p.catch(e => {
-    logger.warn(`withLibCore: Error in job`, e)
-  })
-
-  return p
+  return job(core, walletPool)
 }