diff --git a/package.json b/package.json
index 6e5fc8c..221100d 100644
--- a/package.json
+++ b/package.json
@@ -16,11 +16,11 @@
     "test": "NODE_ENV=test mocha --exit"
   },
   "dependencies": {
-    "@asteasolutions/zod-to-openapi": "^3.4.0"
+    "@asteasolutions/zod-to-openapi": "^4.8.0"
   },
   "peerDependencies": {
     "express": "^5.0.0-beta.1",
-    "openapi3-ts": "^3.2.0",
+    "openapi3-ts": "^4.1.2",
     "zod": "^3"
   },
   "devDependencies": {
@@ -40,7 +40,7 @@
     "express": "^5.0.0-beta.1",
     "husky": "^9.1.7",
     "mocha": "^10.8.2",
-    "openapi3-ts": "^3.2.0",
+    "openapi3-ts": "^4.1.2",
     "pinst": "^3.0.0",
     "semantic-release": "^24.2.0",
     "ts-node": "^10.9.2",
diff --git a/src/openAPI.test.ts b/src/openAPI.test.ts
index d8d7f14..c0fdd04 100644
--- a/src/openAPI.test.ts
+++ b/src/openAPI.test.ts
@@ -1,6 +1,7 @@
 import { expect, spy, use } from "chai";
 import chaiSpies from "chai-spies";
 import { Router } from "express";
+import type { PathItemObject } from "openapi3-ts/oas30";
 import * as schemas from "../mocks/schemas";
 import { buildOpenAPIDocument } from "./openAPI";
 import { openAPIRoute } from "./openAPIRoute";
@@ -104,9 +105,11 @@ describe("buildOpenAPIDocument", () => {
 
     expect(document.paths).to.be.an("object");
     for (const path in document.paths) {
-      for (const method in document.paths[path]) {
-        expect(document.paths[path][method].responses).to.have.property("401");
-        expect(document.paths[path][method].responses).to.have.property("403");
+      for (const key in document.paths[path]) {
+        const method = key as keyof PathItemObject;
+        const { responses } = document.paths[path][method];
+        expect(responses).to.have.property("401");
+        expect(responses).to.have.property("403");
       }
     }
   });
@@ -157,7 +160,8 @@ describe("buildOpenAPIDocument", () => {
     const errors = { 401: "Unauthorized", 403: "Forbidden" };
 
     const document = buildOpenAPIDocument({ config, routers, schemaPaths, errors, openApiVersion });
-    const responseSchema = document.paths["/test"].get.responses["200"].content["application/json"].schema;
+    const method = document.paths["/test"].get;
+    const responseSchema = method!.responses["200"].content["application/json"].schema;
 
     expect(responseSchema.$ref.includes("ResponseSchema")).to.be.true;
   });
@@ -182,7 +186,9 @@ describe("buildOpenAPIDocument", () => {
     const errors = { 401: "Unauthorized", 403: "Forbidden" };
 
     const document = buildOpenAPIDocument({ config, routers, schemaPaths, errors, openApiVersion });
-    const requestBodySchema = document.paths["/test"].get.requestBody.content["application/json"].schema;
+    const method = document.paths["/test"].get;
+    // @ts-ignore
+    const requestBodySchema = method!.requestBody?.content["application/json"].schema;
 
     expect(requestBodySchema.$ref.includes("BodySchema")).to.be.true;
   });
diff --git a/src/openAPI.ts b/src/openAPI.ts
index ec7d30b..6481f02 100644
--- a/src/openAPI.ts
+++ b/src/openAPI.ts
@@ -6,7 +6,7 @@ import {
   RouteConfig,
 } from "@asteasolutions/zod-to-openapi";
 import { RequestHandler, Router } from "express";
-import type { ComponentsObject } from "openapi3-ts";
+import type { ComponentsObject } from "openapi3-ts/oas30";
 import { z, ZodArray, ZodEffects, ZodObject } from "zod";
 import { getSchemaOfOpenAPIRoute } from "./openAPIRoute";
 import { ErrorResponse } from "./schemas";
@@ -201,7 +201,8 @@ export function buildOpenAPIDocument(args: {
   // Verify that none of the "parameters" are appearing as optional, which is invalid
   // in the official OpenAPI spec and unsupported by readme.io
   for (const [route, impl] of Object.entries(openapiJSON.paths)) {
-    for (const method of Object.keys(impl)) {
+    for (const key of Object.keys(impl)) {
+      const method = key as keyof typeof impl;
       for (const param of impl[method].parameters || []) {
         if (param.required === false && param.in === "path") {
           param.required = true;
diff --git a/yarn.lock b/yarn.lock
index b06a1c3..fa3c167 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2,12 +2,12 @@
 # yarn lockfile v1
 
 
-"@asteasolutions/zod-to-openapi@^3.4.0":
-  version "3.4.0"
-  resolved "https://registry.yarnpkg.com/@asteasolutions/zod-to-openapi/-/zod-to-openapi-3.4.0.tgz#7b74b1c32b102048a856b990577f1ebe1861aa18"
-  integrity sha512-xilC2RmsAoJoD0RqZrqArNuC8ByzBIkElIQWEIwreCwSGPHbv2my3d4mnY4x0qQWmSpVnpphEU3Cjl73MpOHjQ==
+"@asteasolutions/zod-to-openapi@^4.8.0":
+  version "4.8.0"
+  resolved "https://registry.yarnpkg.com/@asteasolutions/zod-to-openapi/-/zod-to-openapi-4.8.0.tgz#34c29228c5cd0098a534b3536c9f486fafca2cc1"
+  integrity sha512-FQlBeHIhSoEhjddAWD1v2zbeBESfTdaAVQuUr0RY9t0rN8ogoEaGirv2Ne8kQQTAVGydJzUMAOIlPULEOQDoeA==
   dependencies:
-    openapi3-ts "^3.1.1"
+    openapi3-ts "^4.1.2"
 
 "@babel/code-frame@^7.0.0", "@babel/code-frame@^7.22.13":
   version "7.26.2"
@@ -3432,12 +3432,12 @@ onetime@^6.0.0:
   dependencies:
     mimic-fn "^4.0.0"
 
-openapi3-ts@^3.1.1, openapi3-ts@^3.2.0:
-  version "3.2.0"
-  resolved "https://registry.yarnpkg.com/openapi3-ts/-/openapi3-ts-3.2.0.tgz#7e30d33c480e938e67e809ab16f419bc9beae3f8"
-  integrity sha512-/ykNWRV5Qs0Nwq7Pc0nJ78fgILvOT/60OxEmB3v7yQ8a8Bwcm43D4diaYazG/KBn6czA+52XYy931WFLMCUeSg==
+openapi3-ts@^4.1.2:
+  version "4.4.0"
+  resolved "https://registry.yarnpkg.com/openapi3-ts/-/openapi3-ts-4.4.0.tgz#eff29958e601deec24459ea811989a4fb59d4116"
+  integrity sha512-9asTNB9IkKEzWMcHmVZE7Ts3kC9G7AFHfs8i7caD8HbI76gEjdkId4z/AkP83xdZsH7PLAnnbl47qZkXuxpArw==
   dependencies:
-    yaml "^2.2.1"
+    yaml "^2.5.0"
 
 p-each-series@^3.0.0:
   version "3.0.0"
@@ -4804,7 +4804,7 @@ yallist@^5.0.0:
   resolved "https://registry.yarnpkg.com/yallist/-/yallist-5.0.0.tgz#00e2de443639ed0d78fd87de0d27469fbcffb533"
   integrity sha512-YgvUTfwqyc7UXVMrB+SImsVYSmTS8X/tSrtdNZMImM+n7+QTriRXyXim0mBrTXNeqzVF0KWGgHPeiyViFFrNDw==
 
-yaml@^2.2.1:
+yaml@^2.5.0:
   version "2.6.1"
   resolved "https://registry.yarnpkg.com/yaml/-/yaml-2.6.1.tgz#42f2b1ba89203f374609572d5349fb8686500773"
   integrity sha512-7r0XPzioN/Q9kXBro/XPnA6kznR73DHq+GXh5ON7ZozRO6aMjbmiBuKste2wslTFkC5d1dw0GooOCepZXJ2SAg==