diff --git a/metadata/src/main/java/org/creekservice/api/platform/metadata/ComponentDescriptor.java b/metadata/src/main/java/org/creekservice/api/platform/metadata/ComponentDescriptor.java
index 57f288a..ed05199 100644
--- a/metadata/src/main/java/org/creekservice/api/platform/metadata/ComponentDescriptor.java
+++ b/metadata/src/main/java/org/creekservice/api/platform/metadata/ComponentDescriptor.java
@@ -75,7 +75,7 @@ default Collection<ComponentOutput> outputs() {
      * @return {@link Stream} of component {@link #inputs}, {@link #internals} and {@link #outputs}
      *     resources.
      */
-    default Stream<ResourceDescriptor> resources() {
+    default Stream<? extends ResourceDescriptor> resources() {
         return Stream.concat(
                 inputs().stream(), Stream.concat(internals().stream(), outputs().stream()));
     }
diff --git a/resource/src/test/java/org/creekservice/internal/platform/resource/ComponentValidatorTest.java b/resource/src/test/java/org/creekservice/internal/platform/resource/ComponentValidatorTest.java
index f8627c1..57b7bf8 100644
--- a/resource/src/test/java/org/creekservice/internal/platform/resource/ComponentValidatorTest.java
+++ b/resource/src/test/java/org/creekservice/internal/platform/resource/ComponentValidatorTest.java
@@ -441,7 +441,7 @@ public String dockerImage() {
         }
 
         @Override
-        public Stream<ResourceDescriptor> resources() {
+        public Stream<? extends ResourceDescriptor> resources() {
             return ServiceDescriptor.super.resources();
         }
     }