diff --git a/weed/s3api/s3api_object_handlers.go b/weed/s3api/s3api_object_handlers.go
index 2078d4e69c..877268dfb4 100644
--- a/weed/s3api/s3api_object_handlers.go
+++ b/weed/s3api/s3api_object_handlers.go
@@ -688,11 +688,16 @@ func newListEntry(s3a *S3ApiServer, entry *filer_pb.Entry, key string, dir strin
 	// Determine ETag: prioritize ExtETagKey for versioned objects (supports multipart ETags),
 	// then fall back to filer.ETag() which uses Md5 attribute or calculates from chunks
 	etag := s3a.getObjectETag(entry)
+	size := int64(filer.FileSize(entry))
+	if isDirectory && size == 0 {
+		// A trailing-slash key keeps its body inline in the directory entry, with no FileSize.
+		size = int64(len(entry.Content))
+	}
 	listEntry = ListEntry{
 		Key:          key,
 		LastModified: time.Unix(entry.Attributes.Mtime, 0).UTC(),
 		ETag:         etag,
-		Size:         int64(filer.FileSize(entry)),
+		Size:         size,
 		StorageClass: StorageClass(storageClass),
 	}
 	if fetchOwner {
diff --git a/weed/s3api/s3api_object_handlers_list_directory_marker_test.go b/weed/s3api/s3api_object_handlers_list_directory_marker_test.go
index fe5ab2c7ed..d3b3789761 100644
--- a/weed/s3api/s3api_object_handlers_list_directory_marker_test.go
+++ b/weed/s3api/s3api_object_handlers_list_directory_marker_test.go
@@ -123,3 +123,19 @@ func TestDirectoryMarkersCostNoLookups(t *testing.T) {
 	assert.Equal(t, []string{"d1", "d2", "d3"}, seen)
 	assert.Equal(t, 1, client.calls, "listing directory markers must not cost a round trip per marker")
 }
+
+// TestDirectoryMarkerWithBodyListsItsSize covers a trailing-slash key PUT with a body:
+// the body is kept inline in the directory entry, which has no FileSize, and GET/HEAD
+// already report its length.
+func TestDirectoryMarkerWithBodyListsItsSize(t *testing.T) {
+	s3a := &S3ApiServer{option: &S3ApiServerOption{BucketsPath: "/buckets"}}
+	entry := directoryMarker("m2")
+	entry.Content = []byte("marker body")
+
+	listed := newListEntry(s3a, entry, "", "/buckets/test", "m2", "/buckets/test/", false, true, false)
+	assert.Equal(t, "m2/", listed.Key)
+	assert.Equal(t, int64(len("marker body")), listed.Size)
+
+	listed = newListEntry(s3a, directoryMarker("m3"), "", "/buckets/test", "m3", "/buckets/test/", false, true, false)
+	assert.Equal(t, int64(0), listed.Size)
+}