diff --git a/crates/fayalite/src/sim.rs b/crates/fayalite/src/sim.rs
index 3b55379..6114044 100644
--- a/crates/fayalite/src/sim.rs
+++ b/crates/fayalite/src/sim.rs
@@ -1,3 +1,6 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
 //! Fayalite Simulation
 
 use crate::{
diff --git a/crates/fayalite/src/sim/interpreter.rs b/crates/fayalite/src/sim/interpreter.rs
index 06d0025..f327510 100644
--- a/crates/fayalite/src/sim/interpreter.rs
+++ b/crates/fayalite/src/sim/interpreter.rs
@@ -1,3 +1,6 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
 use crate::{
     intern::{Intern, Interned},
     source_location::SourceLocation,