diff --git a/rest-api-spec/src/main/resources/rest-api-spec/api/cat.segments.json b/rest-api-spec/src/main/resources/rest-api-spec/api/cat.segments.json
index 118f8b6bf9632..3306b2f753b2a 100644
--- a/rest-api-spec/src/main/resources/rest-api-spec/api/cat.segments.json
+++ b/rest-api-spec/src/main/resources/rest-api-spec/api/cat.segments.json
@@ -16,6 +16,11 @@
           "type" : "string",
           "description" : "a short version of the Accept header, e.g. json, yaml"
         },
+        "bytes": {
+          "type": "enum",
+          "description" : "The unit in which to display byte values",
+          "options": [ "b", "k", "kb", "m", "mb", "g", "gb", "t", "tb", "p", "pb" ]
+        },
         "h": {
             "type": "list",
             "description" : "Comma-separated list of column names to display"
diff --git a/rest-api-spec/src/main/resources/rest-api-spec/api/cat.shards.json b/rest-api-spec/src/main/resources/rest-api-spec/api/cat.shards.json
index db46ce909ff6b..2ad714e7225d7 100644
--- a/rest-api-spec/src/main/resources/rest-api-spec/api/cat.shards.json
+++ b/rest-api-spec/src/main/resources/rest-api-spec/api/cat.shards.json
@@ -16,6 +16,11 @@
           "type" : "string",
           "description" : "a short version of the Accept header, e.g. json, yaml"
         },
+        "bytes": {
+          "type": "enum",
+          "description" : "The unit in which to display byte values",
+          "options": [ "b", "k", "kb", "m", "mb", "g", "gb", "t", "tb", "p", "pb" ]
+        },
         "local": {
           "type" : "boolean",
           "description" : "Return local information, do not retrieve the state from master node (default: false)"