diff --git a/byg/src/Evaluation/Function.hs b/byg/src/Evaluation/Function.hs
index 46a0a5c..656a1b3 100644
--- a/byg/src/Evaluation/Function.hs
+++ b/byg/src/Evaluation/Function.hs
@@ -2,7 +2,7 @@ module Evaluation.Function
   ( evalFunction
   ) where
 
-import Types (Function(..))
+import Types (Function(..), Value(..))
 
-evalFunction :: Function -> a -> b
+evalFunction :: Function -> Value -> Value
 evalFunction = undefined
diff --git a/byg/src/Evaluation/FunctionIO.hs b/byg/src/Evaluation/FunctionIO.hs
index aaca9fb..8d39c9f 100644
--- a/byg/src/Evaluation/FunctionIO.hs
+++ b/byg/src/Evaluation/FunctionIO.hs
@@ -2,7 +2,7 @@ module Evaluation.FunctionIO
   ( evalFunctionIO
   ) where
 
-import Types (FunctionIO(..))
+import Types (FunctionIO(..), Value(..))
 
-evalFunctionIO :: FunctionIO -> a -> b
+evalFunctionIO :: FunctionIO -> Value -> IO Value
 evalFunctionIO = undefined