diff --git a/src/namespaced_hash.rs b/src/namespaced_hash.rs
index 2b50bbb..d9eab66 100644
--- a/src/namespaced_hash.rs
+++ b/src/namespaced_hash.rs
@@ -295,7 +295,7 @@ impl<const NS_ID_SIZE: usize> NamespacedHash<NS_ID_SIZE> {
         self.hash
     }
 
-    fn set_hash(&mut self, new_hash: &[u8]) {
+    fn set_hash(&mut self, new_hash: &[u8; HASH_LEN]) {
         self.hash.copy_from_slice(new_hash)
     }