diff --git a/packages/expressjs/src/main/ts/index.ts b/packages/expressjs/src/main/ts/index.ts
index a269985..8cf3490 100644
--- a/packages/expressjs/src/main/ts/index.ts
+++ b/packages/expressjs/src/main/ts/index.ts
@@ -46,8 +46,8 @@ export function JsonRpcMiddleware(): ClassDecorator {
     const extend: Extender = (base) => {
       class Extended extends base {
 
-        @AsyncMiddleware()
-        protected middleware(req: Request, res: Response): any {
+        @AsyncMiddleware
+        protected async middleware(req: Request, res: Response): Promise<any> {
           const boxedJsonRpc = (this.constructor as any).parseRequest(req)
           if (!boxedJsonRpc) {
             // TODO
@@ -64,7 +64,7 @@ export function JsonRpcMiddleware(): ClassDecorator {
               return
             }
 
-            const result = (this.constructor as any).handleResult(handler.apply(this, params))
+            const result = (this.constructor as any).handleResult(await handler.apply(this, params))
             const jsonRpcResponse = result instanceof JsonRpcError
               ? error(id, result)
               : success(id, result)
diff --git a/packages/expressjs/src/test/ts/index.ts b/packages/expressjs/src/test/ts/index.ts
index fe36710..29a57f4 100644
--- a/packages/expressjs/src/test/ts/index.ts
+++ b/packages/expressjs/src/test/ts/index.ts
@@ -27,7 +27,7 @@ describe('expressjs-json-rpc', () => {
 
       middleware: any
       @JsonRpcMethod('test1')
-      bar(@RpcId() id: string) {
+      async bar(@RpcId() id: string) {
         return {foo: 'bar', id}
       }
 
@@ -37,7 +37,7 @@ describe('expressjs-json-rpc', () => {
       }
 
       @JsonRpcMethod('get-some-error')
-      getSomeError() {
+      async getSomeError() {
         return new JsonRpcError('Some error', -100000)
       }