diff --git a/byg/src/DependencyGenerator.hs b/byg/src/DependencyGenerator.hs
index 6f2c129..f9d37fb 100644
--- a/byg/src/DependencyGenerator.hs
+++ b/byg/src/DependencyGenerator.hs
@@ -104,7 +104,7 @@ runFunction f input = genDependency (makeDependency input (Function f))
 runFunctionIO :: IsFunctionIO f a b => f -> Token a -> DepGenM' b
 runFunctionIO f input = genDependency (makeDependency input (FunctionIO f))
 
-runFunctionIO_ :: IsFunctionIO f a b => f -> Token a -> DepGenM ()
+runFunctionIO_ :: IsFunctionIO f a () => f -> Token a -> DepGenM ()
 runFunctionIO_ f input = tellDep $ makeDependency input (FunctionIO f) NoToken
 
 class TokenableTo t s | s -> t where