diff --git a/trustchain-core/src/lib.rs b/trustchain-core/src/lib.rs
index 97819976..e3a510b4 100644
--- a/trustchain-core/src/lib.rs
+++ b/trustchain-core/src/lib.rs
@@ -31,4 +31,5 @@ pub const TRUSTCHAIN_PROOF_SERVICE_ID_VALUE: &str = "trustchain-controller-proof
 /// The value of the type for the service containing a Trustchain controller proof within a DID document.
 pub const TRUSTCHAIN_PROOF_SERVICE_TYPE_VALUE: &str = "TrustchainProofService";
 
+/// String slice for JSON file extension for consistency.
 pub const JSON_FILE_EXTENSION: &str = ".json";