diff --git a/clouddriver-web/src/main/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterController.groovy b/clouddriver-web/src/main/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterController.groovy
index 85c9c36958d..f9244bd3adb 100644
--- a/clouddriver-web/src/main/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterController.groovy
+++ b/clouddriver-web/src/main/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterController.groovy
@@ -79,23 +79,14 @@ class ClusterController {
       .sorted(Comparator.comparing({ Application it -> it.getName().toLowerCase() }))
       .collect(Collectors.toList())
 
-    Map<String, Set<String>> clusterNames = Map.of()
-    def lastApp = null
-    for (app in apps) {
-      if (!lastApp) {
-        clusterNames = app.getClusterNames()
-      } else {
-        clusterNames = mergeClusters(lastApp, app)
-      }
-      lastApp = app
-    }
+    Map<String, Set<String>> clusterNames = mergeClusters(apps)
     return clusterNames
   }
 
-  private Map<String, Set<String>> mergeClusters(Application a, Application b) {
+  private Map<String, Set<String>> mergeClusters(List<Application> a) {
     Map<String, Set<String>> map = new HashMap<>()
 
-    Stream.of(a, b)
+    a.stream()
       .flatMap({ it.getClusterNames().entrySet().stream() })
       .forEach({ entry ->
         map.computeIfAbsent(entry.getKey(), { new HashSet<>() }).addAll(entry.getValue())
diff --git a/clouddriver-web/src/test/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterControllerSpec.groovy b/clouddriver-web/src/test/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterControllerSpec.groovy
index 6a76b5f42f9..bb9480f7e64 100644
--- a/clouddriver-web/src/test/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterControllerSpec.groovy
+++ b/clouddriver-web/src/test/groovy/com/netflix/spinnaker/clouddriver/controllers/ClusterControllerSpec.groovy
@@ -56,13 +56,21 @@ class ClusterControllerSpec extends Specification {
         getApplication("app") >> app2
       }
 
-      clusterController.applicationProviders = [appProvider1, appProvider2]
+      def app3 = Stub(Application) {
+        getName() >> "app"
+        getClusterNames() >> ["stage": ["we-need-all-clusters-to-be-returned"] as Set]
+      }
+      def appProvider3 = Stub(ApplicationProvider) {
+        getApplication("app") >> app3
+      }
+
+      clusterController.applicationProviders = [appProvider1, appProvider2, appProvider3]
 
     when:
       def result = clusterController.listByAccount("app")
 
     then:
-      result == [test: ["foo", "bar"] as Set, prod: ["baz"] as Set]
+      result == [test: ["foo", "bar"] as Set, prod: ["baz"] as Set, stage: ["we-need-all-clusters-to-be-returned"] as Set]
   }
 
   void "should throw exception when looking for specific cluster that doesnt exist"() {