diff --git a/zebra-chain/src/keys/sapling.rs b/zebra-chain/src/keys/sapling.rs
index fb72e5f3..0605a25e 100644
--- a/zebra-chain/src/keys/sapling.rs
+++ b/zebra-chain/src/keys/sapling.rs
@@ -1,3 +1,5 @@
+//! Sapling key types
+
 use std::{
     fmt,
     io::{self},
diff --git a/zebra-chain/src/keys/sprout.rs b/zebra-chain/src/keys/sprout.rs
index c6ffe3e4..583d00fe 100644
--- a/zebra-chain/src/keys/sprout.rs
+++ b/zebra-chain/src/keys/sprout.rs
@@ -1,3 +1,5 @@
+//! Sprout key types
+
 use std::{
     fmt,
     io::{self},