diff --git a/resource/src/main/java/io/wcm/devops/conga/resource/ClasspathResourceCollectionImpl.java b/resource/src/main/java/io/wcm/devops/conga/resource/ClasspathResourceCollectionImpl.java
index 01953e0e..0c954301 100644
--- a/resource/src/main/java/io/wcm/devops/conga/resource/ClasspathResourceCollectionImpl.java
+++ b/resource/src/main/java/io/wcm/devops/conga/resource/ClasspathResourceCollectionImpl.java
@@ -32,7 +32,7 @@
 
 import com.google.common.collect.ImmutableSortedSet;
 
-class ClasspathResourceCollectionImpl extends AbstractClasspathResourceImpl implements ResourceCollection {
+final class ClasspathResourceCollectionImpl extends AbstractClasspathResourceImpl implements ResourceCollection {
 
   private final List<URL> fileUrls = new ArrayList<>();
   private final List<String> folderPaths = new ArrayList<>();