diff --git a/bundles/org.eclipse.equinox.app/src/org/eclipse/equinox/internal/app/AppPersistence.java b/bundles/org.eclipse.equinox.app/src/org/eclipse/equinox/internal/app/AppPersistence.java
index 4e4b672..0181b4a 100644
--- a/bundles/org.eclipse.equinox.app/src/org/eclipse/equinox/internal/app/AppPersistence.java
+++ b/bundles/org.eclipse.equinox.app/src/org/eclipse/equinox/internal/app/AppPersistence.java
@@ -299,6 +299,7 @@
 	// must call this while holding the locks lock
 	private static void saveLocks(File locksData) throws IOException {
 		try (ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(locksData))) {
+			out.writeInt(DATA_VERSION);
 			out.writeInt(locks.size());
 			for (Iterator iterLocks = locks.iterator(); iterLocks.hasNext();)
 				out.writeUTF((String) iterLocks.next());