diff --git a/src/Parser/Interface.md b/src/Parser/Interface.md
index 79583cf..53be055 100644
--- a/src/Parser/Interface.md
+++ b/src/Parser/Interface.md
@@ -110,7 +110,8 @@ Provide wrappers for `rundownFirst` for evaluating it in various contexts.
 
 ```idris
 export
-runFirstIO : (f : Parser a) -> String -> IO (Either ParseError a)
+runFirstIO : HasIO io => MonadRec io =>
+  (f : Parser a) -> String -> io (Either ParseError a)
 runFirstIO f str = do
   Just state <- newInternalIO str
     | _ => pure . Left $ BeforeParse "Empty input"