diff --git a/README.md b/README.md
index 4771d84..3115117 100644
--- a/README.md
+++ b/README.md
@@ -11,13 +11,13 @@
 
 ### Values
 
-    modifyRef :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) {  }
+    modifyRef :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) Unit
 
     newRef :: forall s r. s -> Eff (ref :: Ref | r) (RefVal s)
 
     readRef :: forall s r. RefVal s -> Eff (ref :: Ref | r) s
 
-    writeRef :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) {  }
+    writeRef :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) Unit
 
 
 ## Module Control.Monad.Eff.Ref.Unsafe
diff --git a/src/Control/Monad/Eff/Ref.purs b/src/Control/Monad/Eff/Ref.purs
index 02ce66f..35ea8c3 100644
--- a/src/Control/Monad/Eff/Ref.purs
+++ b/src/Control/Monad/Eff/Ref.purs
@@ -29,7 +29,7 @@ foreign import modifyRef
   \      return {};\
   \    };\
   \  };\
-  \}" :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) {}
+  \}" :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) Unit
 
 foreign import writeRef 
   "function writeRef(ref) {\
@@ -39,4 +39,4 @@ foreign import writeRef
   \      return {};\
   \    };\
   \  };\
-  \}" :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) {}
+  \}" :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) Unit