diff --git a/crates/prolog_parser/src/lexer.rs b/crates/prolog_parser/src/lexer.rs
index b9bda1d0..02053035 100644
--- a/crates/prolog_parser/src/lexer.rs
+++ b/crates/prolog_parser/src/lexer.rs
@@ -33,7 +33,7 @@ macro_rules! consume_chars_with {
     };
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum Token {
     Constant(Constant),
     Var(Rc<Atom>),