diff --git a/cardano-api/src/Cardano/Api/Error.hs b/cardano-api/src/Cardano/Api/Error.hs
index 56ee024b26b..437ad14c4ec 100644
--- a/cardano-api/src/Cardano/Api/Error.hs
+++ b/cardano-api/src/Cardano/Api/Error.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE ExistentialQuantification #-}
 {-# LANGUAGE GADTSyntax #-}
 
@@ -38,7 +39,7 @@ instance Exception ErrorAsException where
     displayException (ErrorAsException e) = displayError e
 
 
-data FileError e = FileError   FilePath e
+data FileError e = FileError FilePath e
                  | FileErrorTempFile
                      FilePath
                      -- ^ Target path
@@ -46,7 +47,7 @@ data FileError e = FileError   FilePath e
                      -- ^ Temporary path
                      Handle
                  | FileIOError FilePath IOException
-  deriving (Show, Eq)
+  deriving (Show, Eq, Functor)
 
 instance Error e => Error (FileError e) where
   displayError (FileErrorTempFile targetPath tempPath h)=
diff --git a/cardano-api/src/Cardano/Api/Keys/Read.hs b/cardano-api/src/Cardano/Api/Keys/Read.hs
index 485e125a835..8570843b064 100644
--- a/cardano-api/src/Cardano/Api/Keys/Read.hs
+++ b/cardano-api/src/Cardano/Api/Keys/Read.hs
@@ -49,18 +49,7 @@ readKeyFileTextEnvelope
   -> FilePath
   -> IO (Either (FileError InputDecodeError) a)
 readKeyFileTextEnvelope asType fp =
-    first toInputDecodeError <$> readFileTextEnvelope asType fp
-  where
-    toInputDecodeError
-      :: FileError TextEnvelopeError
-      -> FileError InputDecodeError
-    toInputDecodeError err =
-      case err of
-        FileIOError path ex -> FileIOError path ex
-        FileError path textEnvErr ->
-          FileError path (InputTextEnvelopeError textEnvErr)
-        FileErrorTempFile targetP tempP h ->
-          FileErrorTempFile targetP tempP h
+    first (fmap InputTextEnvelopeError) <$> readFileTextEnvelope asType fp
 
 -- | Read a cryptographic key from a file given that it is one of the provided
 -- types.