diff --git a/hamming.cabal b/hamming.cabal
index d30e9b9..92d7e18 100644
--- a/hamming.cabal
+++ b/hamming.cabal
@@ -41,6 +41,7 @@ library
       base >=4.7 && <5
     , brick >=2.1.1 && <2.2
     , microlens >=0.4.13.1 && <0.5
+    , microlens-mtl >=0.2.0.3 && <0.3
     , microlens-th >=0.4.3.15 && <0.5
     , mtl >=2.3.1 && <2.4
     , vty ==6.1.*
@@ -60,6 +61,7 @@ executable hamming
     , brick >=2.1.1 && <2.2
     , hamming
     , microlens >=0.4.13.1 && <0.5
+    , microlens-mtl >=0.2.0.3 && <0.3
     , microlens-th >=0.4.3.15 && <0.5
     , mtl >=2.3.1 && <2.4
     , vty ==6.1.*
@@ -88,6 +90,7 @@ test-suite hamming-test
     , hamming
     , hspec >=2.11.9 && <2.12
     , microlens >=0.4.13.1 && <0.5
+    , microlens-mtl >=0.2.0.3 && <0.3
     , microlens-th >=0.4.3.15 && <0.5
     , mtl >=2.3.1 && <2.4
     , vty ==6.1.*
diff --git a/package.yaml b/package.yaml
index fd25673..86b4e00 100644
--- a/package.yaml
+++ b/package.yaml
@@ -22,6 +22,7 @@ dependencies:
 - base >= 4.7 && < 5
 - brick >= 2.1.1 && < 2.2
 - microlens >= 0.4.13.1 && < 0.5
+- microlens-mtl >= 0.2.0.3 && < 0.3
 - microlens-th >= 0.4.3.15 && < 0.5
 - mtl >= 2.3.1 && < 2.4
 - vty >= 6.1 && < 6.2
diff --git a/src/Hamming/App/Events.hs b/src/Hamming/App/Events.hs
index f060ce5..4323743 100644
--- a/src/Hamming/App/Events.hs
+++ b/src/Hamming/App/Events.hs
@@ -30,12 +30,14 @@ module Hamming.App.Events (eventHandler) where
 
 import Brick.Main (halt)
 import Brick.Types (BrickEvent (VtyEvent), gets, modify)
+import Control.Monad.State.Class (put)
 import Graphics.Vty.Input.Events
   ( Event (EvKey)
   , Key (..)
   , Modifier (MCtrl)
   )
 import Lens.Micro ((^.), (.~), (%~))
+import Lens.Micro.Mtl (zoom)
 
 import Hamming
 import Hamming.App.Actions
@@ -46,6 +48,10 @@ eventHandler :: Handler
 eventHandler (VtyEvent (EvKey (KChar 'c') [MCtrl])) = halt
 eventHandler (VtyEvent (EvKey (KChar 'c') [])) =
   modify $ hammingCode %~ setCheckBits
+eventHandler (VtyEvent (EvKey (KChar 'v') [])) =
+  zoom hammingCode $ gets correctErrors >>= \case
+    Just c  -> put c
+    Nothing -> return ()
 eventHandler e = gets (^.appMode) >>= \case
   DisplayMode -> displayHandler e
   EditMode _  -> editHandler e