diff --git a/cardano-crypto-class/src/Cardano/Crypto/EllipticCurve/BLS12_381/Internal.hs b/cardano-crypto-class/src/Cardano/Crypto/EllipticCurve/BLS12_381/Internal.hs
index af956ae41..2eccaa004 100644
--- a/cardano-crypto-class/src/Cardano/Crypto/EllipticCurve/BLS12_381/Internal.hs
+++ b/cardano-crypto-class/src/Cardano/Crypto/EllipticCurve/BLS12_381/Internal.hs
@@ -232,6 +232,10 @@ type Point2 = Point Curve2
 
 newtype Affine curve = Affine (ForeignPtr Void)
 
+-- Making sure different 'Affine's are not 'Coercible', which would ruin the
+-- intended type safety:
+type role Affine nominal
+
 type Affine1 = Affine Curve1
 type Affine2 = Affine Curve2