diff --git a/pkg/reconciler/subscription/subscription.go b/pkg/reconciler/subscription/subscription.go
index e4ed3705dd0..bcbe662b096 100644
--- a/pkg/reconciler/subscription/subscription.go
+++ b/pkg/reconciler/subscription/subscription.go
@@ -196,8 +196,8 @@ func (r *Reconciler) resolveSubscriber(ctx context.Context, subscription *v1.Sub
 	// Resolve Subscriber.
 	subscriber := subscription.Spec.Subscriber.DeepCopy()
 	if !isNilOrEmptyDestination(subscriber) {
-		// Populate the namespace for the subscriber since it is in the namespace
-		if subscriber.Ref != nil {
+		// Populate the namespace for the subscriber if required
+		if subscriber.Ref != nil && subscriber.Ref.Namespace == "" {
 			subscriber.Ref.Namespace = subscription.Namespace
 		}
 
@@ -238,8 +238,8 @@ func (r *Reconciler) resolveReply(ctx context.Context, subscription *v1.Subscrip
 	// Resolve Reply.
 	reply := subscription.Spec.Reply.DeepCopy()
 	if !isNilOrEmptyDestination(reply) {
-		// Populate the namespace for the subscriber since it is in the namespace
-		if reply.Ref != nil {
+		// Populate the namespace for the subscriber if required
+		if reply.Ref != nil && reply.Ref.Namespace == "" {
 			reply.Ref.Namespace = subscription.Namespace
 		}
 		replyURI, err := r.destinationResolver.URIFromDestinationV1(ctx, *reply, subscription)
diff --git a/pkg/reconciler/subscription/subscription_test.go b/pkg/reconciler/subscription/subscription_test.go
index 1f6d69c8b86..566c7b42266 100644
--- a/pkg/reconciler/subscription/subscription_test.go
+++ b/pkg/reconciler/subscription/subscription_test.go
@@ -210,6 +210,138 @@ func TestAllCases(t *testing.T) {
 					MarkSubscriptionReady,
 				),
 			}},
+		}, {
+			Name: "subscription goes ready with subscriber in different namespace",
+			Objects: []runtime.Object{
+				NewSubscription(subscriptionName, testNS,
+					WithSubscriptionUID(subscriptionUID),
+					WithSubscriptionChannel(imcV1GVK, channelName),
+					WithSubscriptionSubscriberRef(subscriberGVK, subscriberName, testNS+"-2"),
+					WithSubscriptionReply(imcV1GVK, replyName, testNS),
+					WithInitSubscriptionConditions,
+					WithSubscriptionFinalizers(finalizerName),
+					MarkReferencesResolved,
+					MarkAddedToChannel,
+					WithSubscriptionPhysicalSubscriptionSubscriber(subscriberURI),
+					WithSubscriptionPhysicalSubscriptionReply(replyURI),
+				),
+				// Subscriber
+				NewUnstructured(subscriberGVK, subscriberName, testNS+"-2",
+					WithUnstructuredAddressable(subscriberDNS),
+				),
+				// Reply
+				NewInMemoryChannel(replyName, testNS,
+					WithInitInMemoryChannelConditions,
+					WithInMemoryChannelAddress(replyDNS),
+				),
+				// Channel
+				NewInMemoryChannel(channelName, testNS,
+					WithInitInMemoryChannelConditions,
+					WithInMemoryChannelReady(channelDNS),
+					WithInMemoryChannelSubscribers([]eventingduck.SubscriberSpec{{
+						UID:           subscriptionUID,
+						Generation:    0,
+						SubscriberURI: subscriberURI,
+						ReplyURI:      replyURI,
+					}, {
+						UID:           "34c5aec8-deb6-11e8-9f32-f2801f1b9fd1",
+						Generation:    1,
+						SubscriberURI: apis.HTTP("call2"),
+						ReplyURI:      apis.HTTP("sink2"),
+					}}),
+					WithInMemoryChannelStatusSubscribers([]eventingduck.SubscriberStatus{{
+						UID:                subscriptionUID,
+						ObservedGeneration: 0,
+						Ready:              "True",
+					}, {
+						UID:                "34c5aec8-deb6-11e8-9f32-f2801f1b9fd1",
+						ObservedGeneration: 1,
+						Ready:              "True",
+					}}),
+				),
+			},
+			Key:     testNS + "/" + subscriptionName,
+			WantErr: false,
+			WantStatusUpdates: []clientgotesting.UpdateActionImpl{{
+				Object: NewSubscription(subscriptionName, testNS,
+					WithSubscriptionUID(subscriptionUID),
+					WithSubscriptionChannel(imcV1GVK, channelName),
+					WithSubscriptionSubscriberRef(subscriberGVK, subscriberName, testNS+"-2"),
+					WithSubscriptionReply(imcV1GVK, replyName, testNS),
+					WithInitSubscriptionConditions,
+					WithSubscriptionFinalizers(finalizerName),
+					WithSubscriptionPhysicalSubscriptionSubscriber(subscriberURI),
+					WithSubscriptionPhysicalSubscriptionReply(replyURI),
+					// - Status Update -
+					MarkSubscriptionReady,
+				),
+			}},
+		}, {
+			Name: "subscription goes ready with reply in different namespace",
+			Objects: []runtime.Object{
+				NewSubscription(subscriptionName, testNS,
+					WithSubscriptionUID(subscriptionUID),
+					WithSubscriptionChannel(imcV1GVK, channelName),
+					WithSubscriptionSubscriberRef(subscriberGVK, subscriberName, testNS),
+					WithSubscriptionReply(imcV1GVK, replyName, testNS+"-2"),
+					WithInitSubscriptionConditions,
+					WithSubscriptionFinalizers(finalizerName),
+					MarkReferencesResolved,
+					MarkAddedToChannel,
+					WithSubscriptionPhysicalSubscriptionSubscriber(subscriberURI),
+					WithSubscriptionPhysicalSubscriptionReply(replyURI),
+				),
+				// Subscriber
+				NewUnstructured(subscriberGVK, subscriberName, testNS,
+					WithUnstructuredAddressable(subscriberDNS),
+				),
+				// Reply
+				NewInMemoryChannel(replyName, testNS+"-2",
+					WithInitInMemoryChannelConditions,
+					WithInMemoryChannelAddress(replyDNS),
+				),
+				// Channel
+				NewInMemoryChannel(channelName, testNS,
+					WithInitInMemoryChannelConditions,
+					WithInMemoryChannelReady(channelDNS),
+					WithInMemoryChannelSubscribers([]eventingduck.SubscriberSpec{{
+						UID:           subscriptionUID,
+						Generation:    0,
+						SubscriberURI: subscriberURI,
+						ReplyURI:      replyURI,
+					}, {
+						UID:           "34c5aec8-deb6-11e8-9f32-f2801f1b9fd1",
+						Generation:    1,
+						SubscriberURI: apis.HTTP("call2"),
+						ReplyURI:      apis.HTTP("sink2"),
+					}}),
+					WithInMemoryChannelStatusSubscribers([]eventingduck.SubscriberStatus{{
+						UID:                subscriptionUID,
+						ObservedGeneration: 0,
+						Ready:              "True",
+					}, {
+						UID:                "34c5aec8-deb6-11e8-9f32-f2801f1b9fd1",
+						ObservedGeneration: 1,
+						Ready:              "True",
+					}}),
+				),
+			},
+			Key:     testNS + "/" + subscriptionName,
+			WantErr: false,
+			WantStatusUpdates: []clientgotesting.UpdateActionImpl{{
+				Object: NewSubscription(subscriptionName, testNS,
+					WithSubscriptionUID(subscriptionUID),
+					WithSubscriptionChannel(imcV1GVK, channelName),
+					WithSubscriptionSubscriberRef(subscriberGVK, subscriberName, testNS),
+					WithSubscriptionReply(imcV1GVK, replyName, testNS+"-2"),
+					WithInitSubscriptionConditions,
+					WithSubscriptionFinalizers(finalizerName),
+					WithSubscriptionPhysicalSubscriptionSubscriber(subscriberURI),
+					WithSubscriptionPhysicalSubscriptionReply(replyURI),
+					// - Status Update -
+					MarkSubscriptionReady,
+				),
+			}},
 		}, {
 			Name: "subscription goes ready without api version",
 			Ctx: feature.ToContext(context.TODO(), feature.Flags{