diff --git a/packages/smithy-client/src/client.ts b/packages/smithy-client/src/client.ts
index 5112a91b3290..516e582624ca 100644
--- a/packages/smithy-client/src/client.ts
+++ b/packages/smithy-client/src/client.ts
@@ -3,6 +3,11 @@ import { Client as IClient, Command, MetadataBearer, RequestHandler } from "@aws
 
 export interface SmithyConfiguration<HandlerOptions> {
   requestHandler: RequestHandler<any, any, HandlerOptions>;
+  /**
+   * The API version set internally by the SDK, and is
+   * not planned to be used by customer code.
+   * @internal
+   */
   readonly apiVersion: string;
 }