diff --git a/docs/sharing-the-cluster/queue-splitting.md b/docs/sharing-the-cluster/queue-splitting.md
index 0a9e8b6..a9a7ee1 100644
--- a/docs/sharing-the-cluster/queue-splitting.md
+++ b/docs/sharing-the-cluster/queue-splitting.md
@@ -474,11 +474,13 @@ spec:
     - directEnvVar:
         container: consumer
         variable: KAFKA_TOPIC_NAME
+        fallback: views-topic # optional, used when the variable is absent
 ```
 
 The topics consumer resource above says that:
 1. It provides context for deployment `meme-app` in namespace `meme`.
 2. The deployment consumes one queue. Its name is read from environment variable `KAFKA_TOPIC_NAME` in container `consumer`.
+If the variable is absent, the fallback value `views-topic` is used instead.
 The Kafka consumer group id is read from environment variable `KAFKA_GROUP_ID` in container `consumer`.
 3. The Kafka queue can be referenced in a mirrord config under ID `views-topic`.
 
@@ -503,8 +505,13 @@ The queues are described in entries of the `spec.topics` list:
 * `id` can be arbitrary, as it will only be [referenced](queue-splitting.md#setting-a-filter-for-a-mirrord-run) from the user's mirrord config.
 * `clientConfig` stores the name of the `MirrordKafkaClientConfig` to use when making connections to the Kafka cluster.
 * `nameSources` stores a list of all occurrences of the queue name in the consumer workload's pod template.
-* `groupIdSources` stores a list of all occurrences of the consumer Kafka group ID in the consumer workload's pod template.
+* `groupIdSources` (required) stores a list of all occurrences of the consumer Kafka group ID in the consumer workload's pod template.
 The operator will use the same group ID when consuming messages from the queue.
+When using `applicationIdSources` instead (Kafka Streams consumers), set this to an empty list `[]`.
+* `applicationIdSources` stores a list of all occurrences of the consumer Kafka Streams application ID in the consumer workload's pod template.
+Relevant only for Kafka Streams consumers. Must be empty if `groupIdSources` is non-empty.
+
+Each source entry supports an optional `fallback` value, used when the specified variable is absent from the workload.
 
 {% hint style="warning" %}
 The mirrord operator can only read consumer's environment variables if they are either: