diff --git a/tz/hash.go b/tz/hash.go
index 018466f..b8b9e50 100644
--- a/tz/hash.go
+++ b/tz/hash.go
@@ -21,7 +21,7 @@ type digest struct {
 }
 
 // type assertion
-var _ hash.Hash = new(digest)
+var _ hash.Hash = (*digest)(nil)
 
 var (
 	minmax  = [2]gf127.GF127{{0, 0}, {math.MaxUint64, math.MaxUint64}}
diff --git a/tz/hash_avx2.go b/tz/hash_avx2.go
index c64a682..5d43516 100644
--- a/tz/hash_avx2.go
+++ b/tz/hash_avx2.go
@@ -10,7 +10,7 @@ type digest2 struct {
 	x [2]gf127.GF127x2
 }
 
-var _ hash.Hash = new(digest2)
+var _ hash.Hash = (*digest2)(nil)
 
 func (d *digest2) Write(data []byte) (n int, err error) {
 	n = len(data)