diff --git a/src/protocol/eval.rs b/src/protocol/eval.rs
index a337ef11a732ee6b50a149b64e7d6ea2c77f31ac..90f093995931cd3c1dab2a90d8b5fd96906a4eb7 100644
--- a/src/protocol/eval.rs
+++ b/src/protocol/eval.rs
@@ -89,6 +89,7 @@ impl Value {
             Literal::Character(_data) => unimplemented!(),
             Literal::Struct(_data) => unimplemented!(),
             Literal::Enum(_data) => unimplemented!(),
+            Literal::Union(_data) => unimplemented!(),
         }
     }
     fn set(&mut self, index: &Value, value: &Value) -> Option<Value> {