diff --git a/ethcore/light/src/client/cht.rs b/ethcore/light/src/cht.rs
similarity index 87%
rename from ethcore/light/src/client/cht.rs
rename to ethcore/light/src/cht.rs
index 8424e0c31..537a3ed6a 100644
--- a/ethcore/light/src/client/cht.rs
+++ b/ethcore/light/src/cht.rs
@@ -20,3 +20,8 @@ pub const SIZE: u64 = 2048;
 pub fn block_to_cht_number(block_num: u64) -> u64 {
 	(block_num + 1) / SIZE
 }
+
+/// Get the starting block of a given CHT.
+pub fn start_number(cht_num: u64) -> u64 {
+	(cht_num * SIZE) + 1
+}
diff --git a/ethcore/light/src/client/header_chain.rs b/ethcore/light/src/client/header_chain.rs
index fdb075e04..a2a953653 100644
--- a/ethcore/light/src/client/header_chain.rs
+++ b/ethcore/light/src/client/header_chain.rs
@@ -28,7 +28,7 @@
 
 use std::collections::{BTreeMap, HashMap};
 
-use client::cht;
+use cht;
 
 use ethcore::block_status::BlockStatus;
 use ethcore::error::BlockError;
diff --git a/ethcore/light/src/client/mod.rs b/ethcore/light/src/client/mod.rs
index 7d4cb0fe8..1d7821e78 100644
--- a/ethcore/light/src/client/mod.rs
+++ b/ethcore/light/src/client/mod.rs
@@ -39,8 +39,6 @@ use self::header_chain::HeaderChain;
 
 pub use self::service::Service;
 
-pub mod cht;
-
 mod header_chain;
 mod service;
 
diff --git a/ethcore/light/src/lib.rs b/ethcore/light/src/lib.rs
index 0e650f992..a23fd879a 100644
--- a/ethcore/light/src/lib.rs
+++ b/ethcore/light/src/lib.rs
@@ -33,6 +33,7 @@
 #![deny(missing_docs)]
 
 pub mod client;
+pub mod cht;
 pub mod net;
 pub mod on_demand;