diff --git a/bundles/org.eclipse.equinox.security.tests/src/org/eclipse/equinox/internal/security/tests/storage/StorageAbstractTest.java b/bundles/org.eclipse.equinox.security.tests/src/org/eclipse/equinox/internal/security/tests/storage/StorageAbstractTest.java
index acdafa37e00..4629cb39247 100644
--- a/bundles/org.eclipse.equinox.security.tests/src/org/eclipse/equinox/internal/security/tests/storage/StorageAbstractTest.java
+++ b/bundles/org.eclipse.equinox.security.tests/src/org/eclipse/equinox/internal/security/tests/storage/StorageAbstractTest.java
@@ -33,7 +33,7 @@ public class StorageAbstractTest {
 
 	final protected String defaultFileName = "secure_storage_test.equinox";
 
-	private List<ISecurePreferences> openPreferences = new ArrayList<>(5); // <ISecurePreferences>
+	private final List<ISecurePreferences> openPreferences = new ArrayList<>(5); // <ISecurePreferences>
 
 	protected String getModuleID() {
 		return null;