diff --git a/package.json b/package.json
index 26933bda..75b27855 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
     "webpack-sources": "1.0.1"
   },
   "dependencies": {
-    "@ledgerhq/hw-app-btc": "^4.13.0",
+    "@ledgerhq/hw-app-btc": "4.20.0",
     "@ledgerhq/hw-app-eth": "^4.14.0",
     "@ledgerhq/hw-app-xrp": "^4.13.0",
     "@ledgerhq/hw-transport": "^4.13.0",
diff --git a/src/commands/libcoreSignAndBroadcast.js b/src/commands/libcoreSignAndBroadcast.js
index 8b8e6bb2..07f36f7a 100644
--- a/src/commands/libcoreSignAndBroadcast.js
+++ b/src/commands/libcoreSignAndBroadcast.js
@@ -77,7 +77,9 @@ async function signTransaction({
   hasTimestamp: boolean,
 }) {
   const additionals = []
+  let expiryHeight
   if (currencyId === 'bitcoin_cash' || currencyId === 'bitcoin_gold') additionals.push('bip143')
+  if (currencyId === 'zcash') expiryHeight = Buffer.from([0x00, 0x00, 0x00, 0x00])
   const rawInputs = transaction.getInputs()
 
   const inputs = await Promise.all(
@@ -119,9 +121,14 @@ async function signTransaction({
 
   const changePath = output ? output.getDerivationPath().toString() : undefined
   const outputScriptHex = Buffer.from(transaction.serializeOutputs()).toString('hex')
-  const lockTime = transaction.getLockTime()
   const initialTimestamp = hasTimestamp ? transaction.getTimestamp() : undefined
 
+  // FIXME
+  // should be `transaction.getLockTime()` as soon as lock time is
+  // handled by libcore (actually: it always returns a default value
+  // and that caused issue with zcash (see #904))
+  const lockTime = undefined
+
   const signedTransaction = await hwApp.createPaymentTransactionNew(
     inputs,
     associatedKeysets,
@@ -132,6 +139,7 @@ async function signTransaction({
     isSegwit,
     initialTimestamp,
     additionals,
+    expiryHeight,
   )
 
   return signedTransaction
diff --git a/yarn.lock b/yarn.lock
index 6a500c91..a7acbc9c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1474,9 +1474,9 @@
   version "0.7.1"
   resolved "https://registry.yarnpkg.com/@emotion/utils/-/utils-0.7.1.tgz#e44e596d03c9f16ba3b127ad333a8a072bcb5a0a"
 
-"@ledgerhq/hw-app-btc@^4.13.0":
-  version "4.19.0"
-  resolved "https://registry.yarnpkg.com/@ledgerhq/hw-app-btc/-/hw-app-btc-4.19.0.tgz#0fdce47ad71df7783c6bf881e6a9bc8b4c84de52"
+"@ledgerhq/hw-app-btc@4.20.0":
+  version "4.20.0"
+  resolved "https://registry.yarnpkg.com/@ledgerhq/hw-app-btc/-/hw-app-btc-4.20.0.tgz#116f841932c199c3a286563831154207a5aa656f"
   dependencies:
     "@ledgerhq/hw-transport" "^4.19.0"
     create-hash "^1.1.3"