diff --git a/opensearch/time_series.go b/opensearch/time_series.go
index 54015d2628a1ae05dd91ff30060b45ea6138440d..be3e3a04659b872c2729dbd9b7ea60da53d43ad9 100644
--- a/opensearch/time_series.go
+++ b/opensearch/time_series.go
@@ -194,6 +194,8 @@ func structMappingProperties(structType reflect.Type) (map[string]MappingPropert
 		case "object":
 			fieldMapping.Type = "object"
 			fieldMapping.Enabled = false
+		case "flattened":
+			fieldMapping.Type = "flat_object"
 		case "-":
 			// do not include in mapping
 			skip = true