diff --git a/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/PartitionWindowedStream.java b/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/PartitionWindowedStream.java
index 7741f3c27b309..744ad4e373442 100644
--- a/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/PartitionWindowedStream.java
+++ b/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/PartitionWindowedStream.java
@@ -77,7 +77,7 @@ <ACC, R> SingleOutputStreamOperator<R> aggregate(
      * KeyedPartitionWindowedStream}, the managed memory size can be set by
      * "execution.sort.keyed.partition.memory" in {@link ExecutionOptions}.
      *
-     * @param field The field index on which records is sorted.
+     * @param field The field 1-based index on which records is sorted.
      * @param order The order in which records is sorted.
      * @return The data stream with sorted records.
      */