diff --git a/sdk/program/src/serde_varint.rs b/sdk/program/src/serde_varint.rs
index 80324bbe0..b7c362e35 100644
--- a/sdk/program/src/serde_varint.rs
+++ b/sdk/program/src/serde_varint.rs
@@ -1,3 +1,5 @@
+//! Integers that serialize to variable size.
+
 #![allow(clippy::integer_arithmetic)]
 use {
     serde::{
diff --git a/sdk/program/src/syscalls/mod.rs b/sdk/program/src/syscalls/mod.rs
index 0d7d28596..740b5457c 100644
--- a/sdk/program/src/syscalls/mod.rs
+++ b/sdk/program/src/syscalls/mod.rs
@@ -1,3 +1,7 @@
+//! Declarations of Solana program syscalls.
+//!
+//! This module is mostly empty when not compiling for BPF targets.
+
 #[cfg(target_os = "solana")]
 mod definitions;