diff --git a/dev/checkstyle/header.txt b/dev/checkstyle/header.txt
index 4e65388..11bd74f 100644
--- a/dev/checkstyle/header.txt
+++ b/dev/checkstyle/header.txt
@@ -1,3 +1,3 @@
 ^/\*$
 ^ \* Copyright [\d]{4}((,[\s]*[\d]{4})*|(-[\d]{4})?) C Thing Software$
-^ \* PDX-License-Identifier: Apache-2.0$
+^ \* SPDX-License-Identifier: Apache-2.0$
diff --git a/src/main/java/org/cthing/gradle/plugins/versioning/VersioningPlugin.java b/src/main/java/org/cthing/gradle/plugins/versioning/VersioningPlugin.java
index 8e9c883..6e027dd 100644
--- a/src/main/java/org/cthing/gradle/plugins/versioning/VersioningPlugin.java
+++ b/src/main/java/org/cthing/gradle/plugins/versioning/VersioningPlugin.java
@@ -1,6 +1,6 @@
 /*
  * Copyright 2024 C Thing Software
- * PDX-License-Identifier: Apache-2.0
+ * SPDX-License-Identifier: Apache-2.0
  */
 
 package org.cthing.gradle.plugins.versioning;
diff --git a/src/main/java/org/cthing/gradle/plugins/versioning/package-info.java b/src/main/java/org/cthing/gradle/plugins/versioning/package-info.java
index 4ca24d7..2aa8624 100644
--- a/src/main/java/org/cthing/gradle/plugins/versioning/package-info.java
+++ b/src/main/java/org/cthing/gradle/plugins/versioning/package-info.java
@@ -1,6 +1,6 @@
 /*
  * Copyright 2024 C Thing Software
- * PDX-License-Identifier: Apache-2.0
+ * SPDX-License-Identifier: Apache-2.0
  */
 
 /**
diff --git a/src/test/java/org/cthing/gradle/plugins/versioning/PluginApplyTest.java b/src/test/java/org/cthing/gradle/plugins/versioning/PluginApplyTest.java
index 270cbf5..5527e9b 100644
--- a/src/test/java/org/cthing/gradle/plugins/versioning/PluginApplyTest.java
+++ b/src/test/java/org/cthing/gradle/plugins/versioning/PluginApplyTest.java
@@ -1,6 +1,6 @@
 /*
  * Copyright 2024 C Thing Software
- * PDX-License-Identifier: Apache-2.0
+ * SPDX-License-Identifier: Apache-2.0
  */
 
 package org.cthing.gradle.plugins.versioning;
diff --git a/src/test/java/org/cthing/gradle/plugins/versioning/PluginIntegTest.java b/src/test/java/org/cthing/gradle/plugins/versioning/PluginIntegTest.java
index 37f7c3b..d9aa42f 100644
--- a/src/test/java/org/cthing/gradle/plugins/versioning/PluginIntegTest.java
+++ b/src/test/java/org/cthing/gradle/plugins/versioning/PluginIntegTest.java
@@ -1,6 +1,6 @@
 /*
  * Copyright 2024 C Thing Software
- * PDX-License-Identifier: Apache-2.0
+ * SPDX-License-Identifier: Apache-2.0
  */
 
 package org.cthing.gradle.plugins.versioning;