diff --git a/typings/index.d.ts b/typings/index.d.ts
index 72521e8..66424a5 100644
--- a/typings/index.d.ts
+++ b/typings/index.d.ts
@@ -3,7 +3,7 @@ declare module "@godaddy/terminus" {
     isShuttingDown: boolean;
   }
 
-  export type HealthCheck = ({ state }: { state: TerminusState }) => Promise<any>;
+  export type HealthCheck = ({ state }: { state: TerminusState }) => Promise<any> | any;
 
   export class HealthCheckError extends Error {
     constructor(message: string, causes: any);
@@ -28,10 +28,10 @@ declare module "@godaddy/terminus" {
     statusError?: number,
     statusErrorResponse?: Record<string, unknown>,
     useExit0?: boolean,
-    onSignal?: () => Promise<any>;
-    onSendFailureDuringShutdown?: () => Promise<any>;
-    onShutdown?: () => Promise<any>;
-    beforeShutdown?: () => Promise<any>;
+    onSignal?: () => Promise<any> | void;
+    onSendFailureDuringShutdown?: () => Promise<any> | void;
+    onShutdown?: () => Promise<any> | void;
+    beforeShutdown?: () => Promise<any> | void;
     logger?: (msg: string, err: Error) => void;
     headers?:{ [key: string]: string };
 
diff --git a/typings/index.test.ts b/typings/index.test.ts
index a151433..230e16e 100644
--- a/typings/index.test.ts
+++ b/typings/index.test.ts
@@ -8,9 +8,13 @@ async function onSignal() {
   ]);
 }
 
-async function onShutdown() {
+async function onShutdownAsync() {
+  console.log('cleanup finished, server is shutting down');
+  return true;
+}
+
+const onShutdown: TerminusOptions["onShutdown"] = () => {
   console.log('cleanup finished, server is shutting down');
-  return Promise.resolve();
 }
 
 const server = http.createServer((request, response) => {
@@ -23,14 +27,25 @@ const healthcheck: HealthCheck = () => {
   throw error;
 }
 
+const healthcheckAsync: HealthCheck = async () => {
+  const result = await Promise.resolve([{ status: 'up' }]);
+  return result;
+}
+
+const healthcheckSync: HealthCheck = () => {
+  return [{ status: 'up' }];
+}
+
 const options: TerminusOptions = {
   healthChecks: {
     "/healthcheck": healthcheck,
+    "/healthcheck-sync": healthcheckSync,
+    "/healthcheck-async": healthcheckAsync,
     verbatim: true
   },
   timeout: 1000,
   onSignal,
-  onShutdown,
+  onShutdown: onShutdownAsync,
   logger: console.log
 };