diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/DownsamplePrepareLifeCycleStateStep.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/DownsamplePrepareLifeCycleStateStep.java
index d935e00be9c42..fa24ca110f665 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/DownsamplePrepareLifeCycleStateStep.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/DownsamplePrepareLifeCycleStateStep.java
@@ -17,6 +17,11 @@
 
 import static org.elasticsearch.xpack.core.ilm.DownsampleAction.DOWNSAMPLED_INDEX_PREFIX;
 
+/**
+ * An ILM step that sets the target index to use in the {@link DownsampleStep}.
+ * The reason why this is done in a seperate step and stored in {@link LifecycleExecutionState},
+ * is because other steps after downsampling also depend on the target index generated here.
+ */
 public class DownsamplePrepareLifeCycleStateStep extends ClusterStateActionStep {
 
     private static final Logger LOGGER = LogManager.getLogger(DownsamplePrepareLifeCycleStateStep.class);