diff --git a/google-cloud-storage/src/main/java/com/google/cloud/storage/ParallelCompositeUploadBlobWriteSessionConfig.java b/google-cloud-storage/src/main/java/com/google/cloud/storage/ParallelCompositeUploadBlobWriteSessionConfig.java
index a5f061e9b3..b93ecd14a8 100644
--- a/google-cloud-storage/src/main/java/com/google/cloud/storage/ParallelCompositeUploadBlobWriteSessionConfig.java
+++ b/google-cloud-storage/src/main/java/com/google/cloud/storage/ParallelCompositeUploadBlobWriteSessionConfig.java
@@ -527,7 +527,7 @@ public static PartNamingStrategy prefix(String prefixPattern) {
      * <p>General format is
      *
      * <pre><code>
-     *   {objectName}/{randomKeyDigest};{objectInfoDigest};{partIndex}.part
+     *   {objectName}-parts/{randomKeyDigest};{objectInfoDigest};{partIndex}.part
      * </code></pre>
      *
      * <p>{@code {objectInfoDigest}} will be fixed for an individual {@link BlobWriteSession}.
@@ -594,6 +594,7 @@ protected String fmtFields(String randomKey, String ultimateObjectName, String p
         String nameDigest = B64.encodeToString(hashCode.asBytes());
         return prefix
             + ultimateObjectName
+            + "-parts"
             + "/"
             + randomKey
             + FIELD_SEPARATOR