diff --git a/byg/src/ComputationM.hs b/byg/src/ComputationM.hs
index c564dd2..c766481 100644
--- a/byg/src/ComputationM.hs
+++ b/byg/src/ComputationM.hs
@@ -75,8 +75,8 @@ genDependency g = do
 inject :: Show a => a -> ComputationM ta a
 inject x = genDependency (Dependency NoToken (TInject x))
 
-runIO :: (Show a, Show b) => FunctionIO a b -> Token t a -> ComputationM TokenNotTraversable b
-runIO f input = genDependency (Dependency input (FIO f))
+runIO :: (Show a, Show b, IsFIO f a b) => f -> Token t a -> ComputationM TokenNotTraversable b
+runIO f input = genDependency (Dependency input (FIO' f))
 
 makeTraversable :: Token TokenNotTraversable [a] -> Token TokenTraversable (Token TokenNotTraversable a)
 makeTraversable (Token n) = Token n
diff --git a/byg/src/Functions.hs b/byg/src/Functions.hs
index d9de92e..a959be6 100644
--- a/byg/src/Functions.hs
+++ b/byg/src/Functions.hs
@@ -34,3 +34,8 @@ data ListDirectory' = ListDirectory'
   deriving (Show)
 instance IsFIO ListDirectory' FilePath [FilePath] where
   runFIO ListDirectory' path = undefined
+
+data OpenImage' = OpenImage'
+  deriving (Show)
+instance IsFIO OpenImage' FilePath Image where
+  runFIO OpenImage' path = undefined
diff --git a/byg/src/Main.hs b/byg/src/Main.hs
index 5c3d2c5..ea4c757 100644
--- a/byg/src/Main.hs
+++ b/byg/src/Main.hs
@@ -6,9 +6,9 @@ import ComputationM
 test :: ComputationM TokenNotTraversable ()
 test = do
   dir <- inject "retter"
-  dirContents <- runIO ListDirectory dir
+  dirContents <- runIO ListDirectory' dir
   let dirContents' = makeTraversable dirContents
-  u <- mapM (runIO OpenImage) dirContents'
+  u <- mapM (runIO OpenImage') dirContents'
   pure $ NoToken
 
 main :: IO ()