diff --git a/src/client.cpp b/src/client.cpp
index 4965916..4a85039 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
 #include <Arduino.h>
 #include <NimBLEDevice.h>
 #include <FastLED.h>
diff --git a/src/ecdh_helper.h b/src/ecdh_helper.h
index edc70de..b9b6d4f 100644
--- a/src/ecdh_helper.h
+++ b/src/ecdh_helper.h
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
 #pragma once
 
 #include <Arduino.h>
diff --git a/src/main.cpp b/src/main.cpp
index f22cbdf..5b6543e 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
 #include <Arduino.h>
 #include <NimBLEDevice.h>
 #include <NimBLEAdvertising.h>