diff --git a/source/reference/operator/aggregation/setIntersection.txt b/source/reference/operator/aggregation/setIntersection.txt
index 12bd9e06c07..31515395899 100644
--- a/source/reference/operator/aggregation/setIntersection.txt
+++ b/source/reference/operator/aggregation/setIntersection.txt
@@ -38,6 +38,9 @@ Behavior
 
 .. include:: /includes/important-set-operator-semantics.rst
 
+If no intersections are found (i.e. the input arrays contain no common
+elements), :expression:`$setIntersection` returns an empty array.
+
 .. include:: /includes/extracts/fact-agg-top-level-expressions-setIntersection.rst
 
 .. list-table::