diff --git a/crypto/bn256/cloudflare/twist.go b/crypto/bn256/cloudflare/twist.go
index 2c7a69a4d7..c048b0b7c7 100644
--- a/crypto/bn256/cloudflare/twist.go
+++ b/crypto/bn256/cloudflare/twist.go
@@ -43,7 +43,7 @@ func (c *twistPoint) Set(a *twistPoint) {
 	c.t.Set(&a.t)
 }
 
-// IsOnCurve returns true iff c is on the curve.
+// IsOnCurve returns true iff c is on the curve and is in the correct subgroup.
 func (c *twistPoint) IsOnCurve() bool {
 	c.MakeAffine()
 	if c.IsInfinity() {
@@ -57,6 +57,9 @@ func (c *twistPoint) IsOnCurve() bool {
 	if *y2 != *x3 {
 		return false
 	}
+	
+	// Subgroup check: multiply the point by the group order and
+	// verify that it becomes the point at infinity.
 	cneg := &twistPoint{}
 	cneg.Mul(c, Order)
 	return cneg.z.IsZero()