diff --git a/mute-interpreter/src/env/core.rs b/mute-interpreter/src/env/core.rs
index 532db68..c1b90db 100644
--- a/mute-interpreter/src/env/core.rs
+++ b/mute-interpreter/src/env/core.rs
@@ -65,6 +65,7 @@ pub(super) fn core() -> HashMap<String, Value> {
         ("-", arithmetic!(-)),
         ("*", arithmetic!(*)),
         ("/", arithmetic!(/)),
+        ("mod", arithmetic!(%)),
         // Ordering
         ("<", ordering!(<)),
         (">", ordering!(>)),