diff --git a/api-ref/source/parameters.yaml b/api-ref/source/parameters.yaml
index 11efb2c3b07a..ea638c3d01ef 100644
--- a/api-ref/source/parameters.yaml
+++ b/api-ref/source/parameters.yaml
@@ -2362,6 +2362,7 @@ flavor_swap:
   description: |
     The size of a dedicated swap disk that will be allocated, in
     MiB. If 0 (the default), no dedicated swap disk will be created.
+    Currently, the empty string ('') is used to represent 0.
   in: body
   required: true
   type: integer