diff --git a/spatial/vptree/vptree.go b/spatial/vptree/vptree.go
index 3b3a3ea..5c94519 100644
--- a/spatial/vptree/vptree.go
+++ b/spatial/vptree/vptree.go
@@ -155,7 +155,7 @@
 
 func (b *builder) random(n int, s []Comparable) []Comparable {
 	if n >= len(s) {
-		return s
+		n = len(s)
 	}
 	b.shuf(len(s), func(i, j int) { s[i], s[j] = s[j], s[i] })
 	return s[:n]