diff --git a/jkube-kit/build/api/src/main/java/org/eclipse/jkube/kit/build/api/assembly/AssemblyFiles.java b/jkube-kit/build/api/src/main/java/org/eclipse/jkube/kit/build/api/assembly/AssemblyFiles.java
index 064f07f3d5..730819c51c 100644
--- a/jkube-kit/build/api/src/main/java/org/eclipse/jkube/kit/build/api/assembly/AssemblyFiles.java
+++ b/jkube-kit/build/api/src/main/java/org/eclipse/jkube/kit/build/api/assembly/AssemblyFiles.java
@@ -29,7 +29,7 @@
 public class AssemblyFiles {
 
     private final File assemblyDirectory;
-    private List<AssemblyFileEntry> entries = new ArrayList<>();
+    private final List<AssemblyFileEntry> entries = new ArrayList<>();
 
     /**
      * Create a collection of assembly files