diff --git a/lib/index.d.ts b/lib/index.d.ts
index 235c471..f22770b 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -183,4 +183,5 @@ export function inject(dispatchFunc: MaybeInjectionListener, options: RequestOpt
  *
  * @return true if the object is a shot request, otherwise false.
  */
+export function isInjection(obj: MaybeInjectedRequest): obj is InjectedRequest;
 export function isInjection(obj: MaybeInjectedRequest | ServerResponse): boolean;
diff --git a/test/index.ts b/test/index.ts
index 9b29f6a..dc0d84c 100644
--- a/test/index.ts
+++ b/test/index.ts
@@ -60,6 +60,13 @@ await Shot.inject((req: Shot.MaybeInjectedRequest, res) => {
     expect.type<boolean>(Shot.isInjection(req));
     expect.type<boolean>(Shot.isInjection(res));
 
+    if (Shot.isInjection(req)) {
+        expect.type<Shot.InjectedRequest>(req);
+    }
+    else {
+        expect.type<IncomingMessage>(req);
+    }
+
     res.end();
 }, '/');