diff --git a/LICENSE b/LICENSE
index 889ccea..9996747 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2023 Fredrik Ekre and Prometheus.jl contributors
+Copyright (c) 2023-2024 Fredrik Ekre and Prometheus.jl contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/src/Prometheus.jl b/src/Prometheus.jl
index f3ff514..a8cd9ab 100644
--- a/src/Prometheus.jl
+++ b/src/Prometheus.jl
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 module Prometheus
 
 using CodecZlib: GzipCompressorStream
diff --git a/src/gc_collector.jl b/src/gc_collector.jl
index e5a15ab..c34a065 100644
--- a/src/gc_collector.jl
+++ b/src/gc_collector.jl
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 ############################
 # GCCollector <: Collector #
 ############################
diff --git a/src/process_collector.jl b/src/process_collector.jl
index 7cbcddf..adce8f5 100644
--- a/src/process_collector.jl
+++ b/src/process_collector.jl
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 #################################
 # ProcessCollector <: Collector #
 #################################
diff --git a/test/runtests.jl b/test/runtests.jl
index 6762d7e..3567be6 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 using HTTP: HTTP
 using Prometheus: Prometheus
 using Test: @test, @test_logs, @test_throws, @testset