diff --git a/types/fb-watchman/fb-watchman-tests.ts b/types/fb-watchman/fb-watchman-tests.ts
index a6f0692278cdd8..717b4677789c3c 100644
--- a/types/fb-watchman/fb-watchman-tests.ts
+++ b/types/fb-watchman/fb-watchman-tests.ts
@@ -211,3 +211,8 @@ client.on("subscription", (resp) => {
         }
     });
 });
+
+// All commands should accept a callback, including "unofficial" ones
+client.command(["watch-del", "/"], () => {});
+// .. and it's optional
+client.command(["watch-del-all"]);
diff --git a/types/fb-watchman/index.d.ts b/types/fb-watchman/index.d.ts
index 4c6553993f4d2a..28c517762394f8 100644
--- a/types/fb-watchman/index.d.ts
+++ b/types/fb-watchman/index.d.ts
@@ -383,6 +383,7 @@ export class Client extends EventEmitter {
             ),
             ...any[],
         ],
+        callback?: CommandCallback,
     ): void;
 
     /**