diff --git a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSource.java b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSource.java
index 6180656e55..6dbf5b7fb4 100644
--- a/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSource.java
+++ b/operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSource.java
@@ -238,7 +238,7 @@ public synchronized void handleRecentResourceUpdate(
     if (actualValues != null) {
       var resourceId = resourceIDMapper.idFor(resource);
       R actualResource = actualValues.get(resourceId);
-      if (actualResource.equals(previousVersionOfResource)) {
+      if (actualResource != null && actualResource.equals(previousVersionOfResource)) {
         actualValues.put(resourceId, resource);
       }
     }
diff --git a/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSourceTest.java b/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSourceTest.java
index 6fe97b2fdd..024bd95dfc 100644
--- a/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSourceTest.java
+++ b/operator-framework-core/src/test/java/io/javaoperatorsdk/operator/processing/event/source/ExternalResourceCachingEventSourceTest.java
@@ -212,6 +212,16 @@ void genericFilteringEvents() {
   }
 
   @Test
+  void recentResourceUpdateIsIgnoredForUnknownSecondaryResource() {
+    source.handleResources(primaryID1(), Set.of(testResource1()));
+
+    // testResource2 has a different id, so it is not present in the cache for primaryID1
+    var unknown = testResource2();
+    source.handleRecentResourceUpdate(primaryID1(), unknown, unknown);
+
+    assertThat(source.getSecondaryResources(primaryID1())).containsExactly(testResource1());
+  }
+
   void onlyGenericFilterSetDoesNotFailOnAdd() {
     var eventSource = new TestExternalCachingEventSource();
     eventSource.setGenericFilter(res -> true);