diff --git a/iris_heap_lang/lang.v b/iris_heap_lang/lang.v
index f435cb81c792230cadb7fe30e5e8013bb590bcdc..6a126402e27acbf9923eb42d97156476c3067bac 100644
--- a/iris_heap_lang/lang.v
+++ b/iris_heap_lang/lang.v
@@ -79,6 +79,9 @@ Inductive base_lit : Set :=
 Inductive un_op : Set :=
   | NegOp | MinusUnOp.
 Inductive bin_op : Set :=
+  (** We use "quot" and "rem" instead of "div" and "mod" to
+      better match the behavior of 'real' languages:
+      -30/-4 == 7. ("div" would return 8.) *)
   | PlusOp | MinusOp | MultOp | QuotOp | RemOp (* Arithmetic *)
   | AndOp | OrOp | XorOp (* Bitwise *)
   | ShiftLOp | ShiftROp (* Shifts *)