diff --git a/clients/client-workspaces/src/models/models_0.ts b/clients/client-workspaces/src/models/models_0.ts
index 6e8ae76922288..d4f194a68cd64 100644
--- a/clients/client-workspaces/src/models/models_0.ts
+++ b/clients/client-workspaces/src/models/models_0.ts
@@ -2326,6 +2326,7 @@ export interface WorkspaceRequest {
 
   /**
    * <p>The user name of the user for the WorkSpace. This user name must exist in the Directory Service directory for the WorkSpace.</p>
+   *          <p>The username is not case-sensitive, but we recommend matching the case in the Directory Service directory to avoid potential incompatibilities.</p>
    *          <p>The reserved keyword, <code>[UNDEFINED]</code>, is used when creating user-decoupled WorkSpaces.</p>
    * @public
    */
diff --git a/codegen/sdk-codegen/aws-models/workspaces.json b/codegen/sdk-codegen/aws-models/workspaces.json
index 749228d7e0422..e30232bb7a358 100644
--- a/codegen/sdk-codegen/aws-models/workspaces.json
+++ b/codegen/sdk-codegen/aws-models/workspaces.json
@@ -11152,7 +11152,7 @@
         "UserName": {
           "target": "com.amazonaws.workspaces#UserName",
           "traits": {
-            "smithy.api#documentation": "<p>The user name of the user for the WorkSpace. This user name must exist in the Directory Service directory for the WorkSpace.</p>\n         <p>The reserved keyword, <code>[UNDEFINED]</code>, is used when creating user-decoupled WorkSpaces.</p>",
+            "smithy.api#documentation": "<p>The user name of the user for the WorkSpace. This user name must exist in the Directory Service directory for the WorkSpace.</p>\n         <p>The username is not case-sensitive, but we recommend matching the case in the Directory Service directory to avoid potential incompatibilities.</p>\n         <p>The reserved keyword, <code>[UNDEFINED]</code>, is used when creating user-decoupled WorkSpaces.</p>",
             "smithy.api#required": {}
           }
         },