diff --git a/src/dict.rs b/src/dict.rs
index 83b63ee..93bb6ec 100644
--- a/src/dict.rs
+++ b/src/dict.rs
@@ -2,7 +2,7 @@ use crate::bimap::Bimap;
 
 //<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>\\
 
-#[derive(Eq, PartialEq, Hash, Clone, Debug)]
+#[derive(Eq, PartialEq, Hash, Clone, Copy, Debug)]
 pub enum TypeID {
     Fun(u64),
     Var(u64)