diff --git a/src/ZcashHaskell/Keys.hs b/src/ZcashHaskell/Keys.hs
index 261020f..8f00c3b 100644
--- a/src/ZcashHaskell/Keys.hs
+++ b/src/ZcashHaskell/Keys.hs
@@ -99,7 +99,7 @@ deriveUfvk ::
   -> OrchardSpendingKey
   -> SaplingSpendingKey
   -> TransparentSpendingKey
-  -> IO T.Text
+  -> IO ValidVk
 deriveUfvk net okey skey tkey = do
   tSec <- deriveFullTransparentNode tkey
   let oSec = deriveOrchardFvk okey
@@ -111,7 +111,6 @@ deriveUfvk net okey skey tkey = do
         Nothing -> fail "Unable to derive Sapling viewing key"
         Just sSec' ->
           return $
-          encodeVK $
           FullVk $
           UnifiedFullViewingKey
             (case net of
@@ -127,7 +126,7 @@ deriveUivk ::
   -> OrchardSpendingKey
   -> SaplingSpendingKey
   -> TransparentSpendingKey
-  -> IO T.Text
+  -> IO ValidVk
 deriveUivk net okey skey tkey = do
   tSec <- deriveIncomingTransparentNode tkey
   let oSec = deriveOrchardIvk okey
@@ -139,7 +138,6 @@ deriveUivk net okey skey tkey = do
         Nothing -> fail "Unable to derive Sapling viewing key"
         Just sSec' ->
           return $
-          encodeVK $
           IncomingVk $
           UnifiedIncomingViewingKey
             (case net of