diff --git a/src/cst/tags.rs b/src/cst/tags.rs
index 4a1f799..383c8ea 100644
--- a/src/cst/tags.rs
+++ b/src/cst/tags.rs
@@ -107,4 +107,5 @@ impl Tag {
 
     pub const BINARY_ADD: &'static str = "&";
     pub const BINARY_OR: &'static str = "|";
+    pub const UNARY_NOT: &'static str = "~";
 }