diff --git a/allowed-breaking-changes.txt b/allowed-breaking-changes.txt
index 56b1145d61b39..599cc80596857 100644
--- a/allowed-breaking-changes.txt
+++ b/allowed-breaking-changes.txt
@@ -115,4 +115,9 @@ removed:@aws-cdk/aws-lambda-event-sources.SelfManagedKafkaEventSourceProps.retry
 removed:@aws-cdk/aws-lambda-event-sources.SelfManagedKafkaEventSourceProps.tumblingWindow
 base-types:@aws-cdk/aws-lambda-event-sources.KafkaEventSourceProps
 base-types:@aws-cdk/aws-lambda-event-sources.ManagedKafkaEventSourceProps
-base-types:@aws-cdk/aws-lambda-event-sources.SelfManagedKafkaEventSourceProps
\ No newline at end of file
+base-types:@aws-cdk/aws-lambda-event-sources.SelfManagedKafkaEventSourceProps
+
+# fixed vpc property of BaseLoadBalancer so it correctly implements I(Application|Network)LoadBalancer (i.e: must be optional)
+changed-type:@aws-cdk/aws-elasticloadbalancingv2.ApplicationLoadBalancer.vpc
+changed-type:@aws-cdk/aws-elasticloadbalancingv2.BaseLoadBalancer.vpc
+changed-type:@aws-cdk/aws-elasticloadbalancingv2.NetworkLoadBalancer.vpc
diff --git a/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/shared/base-load-balancer.ts b/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/shared/base-load-balancer.ts
index 85ae9d143f0e2..345583bf9e5f8 100644
--- a/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/shared/base-load-balancer.ts
+++ b/packages/@aws-cdk/aws-elasticloadbalancingv2/lib/shared/base-load-balancer.ts
@@ -192,8 +192,11 @@ export abstract class BaseLoadBalancer extends Resource {
 
   /**
    * The VPC this load balancer has been created in.
+   *
+   * This property is always defined (not `null` or `undefined`) for sub-classes of `BaseLoadBalancer`.
    */
-  public readonly vpc: ec2.IVpc;
+  public readonly vpc?: ec2.IVpc;
+
   /**
    * Attributes set on this load balancer
    */