diff --git a/api-ref/source/v2/parameters.yaml b/api-ref/source/v2/parameters.yaml
index 5164366f17e..4dd0814a86d 100644
--- a/api-ref/source/v2/parameters.yaml
+++ b/api-ref/source/v2/parameters.yaml
@@ -1490,7 +1490,7 @@ snapshot_id_2:
   description: |
     The UUID of the source volume snapshot.
   in: body
-  required: true
+  required: false
   type: string
 source_cgid:
   description: |
diff --git a/api-ref/source/v3/ext-backups.inc b/api-ref/source/v3/ext-backups.inc
index 81a8ebbef8a..8f02b00c4bb 100644
--- a/api-ref/source/v3/ext-backups.inc
+++ b/api-ref/source/v3/ext-backups.inc
@@ -263,7 +263,7 @@ Create a backup
 
 .. rest_method::  POST /v3/{project_id}/backups
 
-Creates a Block Storage backup from a volume.
+Creates a Block Storage backup from a volume or snapshot.
 
 Response codes
 --------------
diff --git a/api-ref/source/v3/parameters.yaml b/api-ref/source/v3/parameters.yaml
index 19ec5b27682..7321023b490 100644
--- a/api-ref/source/v3/parameters.yaml
+++ b/api-ref/source/v3/parameters.yaml
@@ -2423,11 +2423,9 @@ snapshot_id_2:
   type: string
 snapshot_id_3:
   description: |
-    The UUID of the source volume snapshot. The API
-    creates a new volume snapshot with the same size as the source
-    volume snapshot unless a larger size is requested.
+    The UUID of the source snapshot that you want to back up.
   in: body
-  required: true
+  required: false
   type: string
 snapshot_id_4:
   description: |