diff --git a/lib/core/src/Cardano/Wallet/Api/Server.hs b/lib/core/src/Cardano/Wallet/Api/Server.hs
index 1d3ce51f752..b05a473650c 100644
--- a/lib/core/src/Cardano/Wallet/Api/Server.hs
+++ b/lib/core/src/Cardano/Wallet/Api/Server.hs
@@ -491,7 +491,7 @@ instance LiftHandler ErrSignTx where
         ErrSignTx ErrInvalidTx ->
             apiError err403 CreatedInvalidTransaction $ mconcat
                 [ "I can't process this payment because transactions"
-                , " with 0 amount are not supported in Shelley."
+                , " with 0 amount are not supported in Byron."
                 ]
         ErrSignTxNoSuchWallet e -> (handler e)
             { errHTTPCode = 410
diff --git a/lib/core/test/integration/Test/Integration/Framework/TestData.hs b/lib/core/test/integration/Test/Integration/Framework/TestData.hs
index 6dd24715580..47e5808f7b5 100644
--- a/lib/core/test/integration/Test/Integration/Framework/TestData.hs
+++ b/lib/core/test/integration/Test/Integration/Framework/TestData.hs
@@ -223,7 +223,7 @@ errMsg403NotEnoughMoney has needs = "I can't process this payment because there'
 
 errMsg403InvalidTransaction :: String
 errMsg403InvalidTransaction = "I can't process this payment because transactions\
-    \ with 0 amount are not supported in Shelley."
+    \ with 0 amount are not supported in Byron."
 
 errMsg403UTxO :: String
 errMsg403UTxO = "When creating new transactions, I'm not able to re-use the\
diff --git a/lib/http-bridge/src/Cardano/Wallet/HttpBridge/Transaction.hs b/lib/http-bridge/src/Cardano/Wallet/HttpBridge/Transaction.hs
index 479a386e800..a86e66aa23e 100644
--- a/lib/http-bridge/src/Cardano/Wallet/HttpBridge/Transaction.hs
+++ b/lib/http-bridge/src/Cardano/Wallet/HttpBridge/Transaction.hs
@@ -32,7 +32,7 @@ import Cardano.Wallet.Primitive.Types
 import Cardano.Wallet.Transaction
     ( ErrMkStdTx (..), TransactionLayer (..) )
 import Control.Monad
-    ( forM, when )
+    ( forM, unless )
 import Data.ByteString
     ( ByteString )
 import Data.Either.Combinators
@@ -54,7 +54,7 @@ newTransactionLayer = TransactionLayer
     { mkStdTx = \keyFrom inps outs -> do
         let ins = (fmap fst inps)
         let tx = Tx ins outs
-        when (not . null $ filter (\(TxOut _ c) -> c == Coin 0) outs)
+        unless (not (any (\ (TxOut _ c) -> c == Coin 0) outs))
             $ Left ErrInvalidTx
         -- Not working, maybe we need to make TransactionLayer polymorphic
         let txSigData = txId @(HttpBridge n) tx