diff --git a/src/config.rs b/src/config.rs
index 351650b..9397506 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -13,6 +13,7 @@ pub enum Error {
 
 #[derive(Debug)]
 pub enum ParseError {
+    // u32 is the line number where an error occured
     UnknownSymbol(u32),
     MissingCommand(u32),
 }