diff --git a/docs/lib3x-polyline_join.md b/docs/lib3x-polyline_join.md
index 46bfc6a8..5a6c37ed 100644
--- a/docs/lib3x-polyline_join.md
+++ b/docs/lib3x-polyline_join.md
@@ -2,6 +2,8 @@
 
 Place a join on each point. Hull each pair of joins and union all convex hulls.
 
+**Since:** 3.2
+
 ## Parameters
 
 - `points` : a list of points.