diff --git a/Changelog.md b/Changelog.md
index c8e3f5b2..e5c53317 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -18,6 +18,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Changed Home page to display globals for HTML format.
   #81 by @kean.
+- Changed README to clarify use of `swift-doc` vs. `swift doc`
+  on the command line.
+  #89 by @mattt.
 
 ### Fixed
 
diff --git a/README.md b/README.md
index 80d23add..ff8b669d 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,12 @@ $ make install
                               files
       diagram                 Generates diagram of Swift symbol relationships
 
+> **Note**:
+> The `swift` driver provides extensibility through subcommands.
+> If you type an unknown subcommand like `swift foo`,
+> the system looks for a command called `swift-foo` in your `PATH`.
+> This mechanism allows `swift-doc` to be run either directly or as `swift doc`.
+
 #### swift-doc generate
 
     OVERVIEW: Generates Swift documentation