diff --git a/src/main/python/constants.py b/src/main/python/constants.py
index 224eafb..43563fe 100644
--- a/src/main/python/constants.py
+++ b/src/main/python/constants.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 KEY_WIDTH = 40
 KEY_HEIGHT = KEY_WIDTH
 KEY_SPACING = 4
diff --git a/src/main/python/keyboard_container.py b/src/main/python/keyboard_container.py
index bceff3f..1a50b9c 100644
--- a/src/main/python/keyboard_container.py
+++ b/src/main/python/keyboard_container.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 from collections import defaultdict
 
 from PyQt5.QtCore import pyqtSignal, Qt
diff --git a/src/main/python/main_window.py b/src/main/python/main_window.py
index a84a79c..2b6b288 100644
--- a/src/main/python/main_window.py
+++ b/src/main/python/main_window.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 from PyQt5.QtCore import Qt
 from PyQt5.QtWidgets import QWidget, QComboBox, QToolButton, QHBoxLayout, QVBoxLayout
 
diff --git a/src/main/python/tabbed_keycodes.py b/src/main/python/tabbed_keycodes.py
index ec935ec..cc2f1ba 100644
--- a/src/main/python/tabbed_keycodes.py
+++ b/src/main/python/tabbed_keycodes.py
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
 from PyQt5.QtCore import Qt, pyqtSignal
 from PyQt5.QtWidgets import QTabWidget, QWidget, QPushButton, QScrollArea