diff --git a/application.ts b/application.ts
index e4ff02de..fed8ece7 100644
--- a/application.ts
+++ b/application.ts
@@ -547,7 +547,7 @@ export class Application<AS extends State = Record<string, any>>
    * context gets set to not to respond, then the method resolves with
    * `undefined`, otherwise it resolves with a request that is compatible with
    * `std/http/server`. */
-  handle = (async (
+  handle: HandleMethod = (async (
     request: Request,
     secureOrAddr: NetAddr | boolean | undefined,
     secure: boolean | undefined = false,
@@ -582,7 +582,7 @@ export class Application<AS extends State = Record<string, any>>
       this.#handleError(context, err);
       throw err;
     }
-  }) as HandleMethod;
+  });
 
   /** Start listening for requests, processing registered middleware on each
    * request.  If the options `.secure` is undefined or `false`, the listening
@@ -697,7 +697,9 @@ export class Application<AS extends State = Record<string, any>>
     return this as Application<any>;
   }
 
-  [Symbol.for("Deno.customInspect")](inspect: (value: unknown) => string) {
+  [Symbol.for("Deno.customInspect")](
+    inspect: (value: unknown) => string,
+  ): string {
     const { keys, proxy, state } = this;
     return `${this.constructor.name} ${
       inspect({ "#middleware": this.#middleware, keys, proxy, state })
@@ -709,7 +711,8 @@ export class Application<AS extends State = Record<string, any>>
     // deno-lint-ignore no-explicit-any
     options: any,
     inspect: (value: unknown, options?: unknown) => string,
-  ) {
+    // deno-lint-ignore no-explicit-any
+  ): any {
     if (depth < 0) {
       return options.stylize(`[${this.constructor.name}]`, "special");
     }
diff --git a/context.ts b/context.ts
index c5dfab50..cd36d5bc 100644
--- a/context.ts
+++ b/context.ts
@@ -305,7 +305,9 @@ export class Context<
     return this.#socket;
   }
 
-  [Symbol.for("Deno.customInspect")](inspect: (value: unknown) => string) {
+  [Symbol.for("Deno.customInspect")](
+    inspect: (value: unknown) => string,
+  ): string {
     const {
       app,
       cookies,
@@ -335,7 +337,8 @@ export class Context<
     // deno-lint-ignore no-explicit-any
     options: any,
     inspect: (value: unknown, options?: unknown) => string,
-  ) {
+    // deno-lint-ignore no-explicit-any
+  ): any {
     if (depth < 0) {
       return options.stylize(`[${this.constructor.name}]`, "special");
     }
diff --git a/http_server_native.ts b/http_server_native.ts
index e1c2af11..2e806a62 100644
--- a/http_server_native.ts
+++ b/http_server_native.ts
@@ -12,17 +12,6 @@ import type {
 } from "./types.ts";
 import { createPromiseWithResolvers } from "./util.ts";
 
-// this is included so when down-emitting to npm/Node.js, ReadableStream has
-// async iterators
-declare global {
-  // deno-lint-ignore no-explicit-any
-  interface ReadableStream<R = any> {
-    [Symbol.asyncIterator](options?: {
-      preventCancel?: boolean;
-    }): AsyncIterableIterator<R>;
-  }
-}
-
 const serve: (
   options: ServeInit & (ServeOptions | ServeTlsOptions),
 ) => HttpServer = "serve" in Deno
diff --git a/range.ts b/range.ts
index 71625818..310283a2 100644
--- a/range.ts
+++ b/range.ts
@@ -163,7 +163,7 @@ export class MultiPartStream extends ReadableStream<Uint8Array> {
   }
 
   /** The content length of the entire streamed body. */
-  contentLength() {
+  contentLength(): number {
     return this.#contentLength;
   }
 }
diff --git a/request.ts b/request.ts
index 567e928c..e85756c4 100644
--- a/request.ts
+++ b/request.ts
@@ -251,7 +251,9 @@ export class Request {
     return this.#serverRequest.upgrade(options);
   }
 
-  [Symbol.for("Deno.customInspect")](inspect: (value: unknown) => string) {
+  [Symbol.for("Deno.customInspect")](
+    inspect: (value: unknown) => string,
+  ): string {
     const { body, hasBody, headers, ip, ips, method, secure, url, userAgent } =
       this;
     return `${this.constructor.name} ${
@@ -274,7 +276,8 @@ export class Request {
     // deno-lint-ignore no-explicit-any
     options: any,
     inspect: (value: unknown, options?: unknown) => string,
-  ) {
+    // deno-lint-ignore no-explicit-any
+  ): any {
     if (depth < 0) {
       return options.stylize(`[${this.constructor.name}]`, "special");
     }
diff --git a/response.ts b/response.ts
index 60af5ddc..59c30a63 100644
--- a/response.ts
+++ b/response.ts
@@ -361,7 +361,9 @@ export class Response {
       : new DomResponse(responseOrBody, init);
   }
 
-  [Symbol.for("Deno.customInspect")](inspect: (value: unknown) => string) {
+  [Symbol.for("Deno.customInspect")](
+    inspect: (value: unknown) => string,
+  ): string {
     const { body, headers, status, type, writable } = this;
     return `${this.constructor.name} ${
       inspect({ body, headers, status, type, writable })
@@ -373,7 +375,8 @@ export class Response {
     // deno-lint-ignore no-explicit-any
     options: any,
     inspect: (value: unknown, options?: unknown) => string,
-  ) {
+    // deno-lint-ignore no-explicit-any
+  ): any {
     if (depth < 0) {
       return options.stylize(`[${this.constructor.name}]`, "special");
     }
diff --git a/router.ts b/router.ts
index 56c13332..fa1cb012 100644
--- a/router.ts
+++ b/router.ts
@@ -300,7 +300,7 @@ export class Layer<
 
   params(
     captures: string[],
-    existingParams = {} as RouteParams<R>,
+    existingParams: RouteParams<R> = {} as RouteParams<R>,
   ): RouteParams<R> {
     const params = existingParams;
     for (let i = 0; i < captures.length; i++) {
@@ -320,7 +320,7 @@ export class Layer<
   }
 
   url(
-    params = {} as RouteParams<R>,
+    params: RouteParams<R> = {} as RouteParams<R>,
     options?: UrlOptions,
   ): string {
     const url = this.path.replace(/\(\.\*\)/g, "");
@@ -331,7 +331,7 @@ export class Layer<
     param: string,
     // deno-lint-ignore no-explicit-any
     fn: RouterParamMiddleware<any, any, any>,
-  ) {
+  ): this {
     const stack = this.stack;
     const params = this.#paramNames;
     const middleware: RouterMiddleware<R> = function (
@@ -383,7 +383,9 @@ export class Layer<
     };
   }
 
-  [Symbol.for("Deno.customInspect")](inspect: (value: unknown) => string) {
+  [Symbol.for("Deno.customInspect")](
+    inspect: (value: unknown) => string,
+  ): string {
     return `${this.constructor.name} ${
       inspect({
         methods: this.methods,
@@ -401,7 +403,8 @@ export class Layer<
     // deno-lint-ignore no-explicit-any
     options: any,
     inspect: (value: unknown, options?: unknown) => string,
-  ) {
+    // deno-lint-ignore no-explicit-any
+  ): any {
     if (depth < 0) {
       return options.stylize(`[${this.constructor.name}]`, "special");
     }
@@ -1400,7 +1403,9 @@ export class Router<
     return toUrl(path, params, options);
   }
 
-  [Symbol.for("Deno.customInspect")](inspect: (value: unknown) => string) {
+  [Symbol.for("Deno.customInspect")](
+    inspect: (value: unknown) => string,
+  ): string {
     return `${this.constructor.name} ${
       inspect({ "#params": this.#params, "#stack": this.#stack })
     }`;
@@ -1411,7 +1416,8 @@ export class Router<
     // deno-lint-ignore no-explicit-any
     options: any,
     inspect: (value: unknown, options?: unknown) => string,
-  ) {
+    // deno-lint-ignore no-explicit-any
+  ): any {
     if (depth < 0) {
       return options.stylize(`[${this.constructor.name}]`, "special");
     }
diff --git a/testing.ts b/testing.ts
index 42099c4f..9d225a51 100644
--- a/testing.ts
+++ b/testing.ts
@@ -24,7 +24,7 @@ import { Response } from "./response.ts";
 export function createMockApp<
   S extends Record<string | number | symbol, any> = Record<string, any>,
 >(
-  state = {} as S,
+  state: S = {} as S,
 ): Application<S> {
   const app = {
     state,
@@ -91,7 +91,7 @@ export function createMockContext<
     app = createMockApp(state),
     headers: requestHeaders,
   }: MockContextOptions<R> = {},
-) {
+): RouterContext<R, P, S> {
   function createMockRequest(): Request {
     const headers = new Headers(requestHeaders);
     return {
@@ -178,6 +178,6 @@ export function createMockContext<
 
 /** Creates a mock `next()` function which can be used when calling
  * middleware. */
-export function createMockNext() {
+export function createMockNext(): () => Promise<void> {
   return async function next() {};
 }