diff --git a/src/lib/structures/expr.ml b/src/lib/structures/expr.ml
index c19347c4a..463ffa74e 100644
--- a/src/lib/structures/expr.ml
+++ b/src/lib/structures/expr.ml
@@ -95,6 +95,11 @@ and semantic_trigger =
 
 and trigger = {
   content : t list;
+  (* [content] must be kept sorted in [pat_weight] (see below) order for
+     matching.
+
+     [mk_trigger] enforces this, but functions that modify [content] and must
+     preserve this order. *)
   semantic : semantic_trigger list;
   hyp : t list;
   t_depth : int;
diff --git a/tests/issues/1111.expected b/tests/issues/1111.expected
index e69de29bb..a6e005255 100644
--- a/tests/issues/1111.expected
+++ b/tests/issues/1111.expected
@@ -0,0 +1,2 @@
+
+unknown