diff --git a/src/core/index.js b/src/core/index.js
index c839ca61..0af27ee4 100644
--- a/src/core/index.js
+++ b/src/core/index.js
@@ -37,6 +37,7 @@ module.exports = function SwaggerUI(opts) {
     maxDisplayedTags: null,
     filter: null,
     validatorUrl: "https://online.swagger.io/validator",
+    oauth2RedirectUrl: `${window.location.protocol}//${window.location.host}/oauth2-redirect.html`,
     configs: {},
     custom: {},
     displayOperationId: false,
diff --git a/swagger-config.yaml b/swagger-config.yaml
index 52ae525a..70d2719d 100644
--- a/swagger-config.yaml
+++ b/swagger-config.yaml
@@ -1,5 +1,4 @@
 ---
 url: "https://petstore.swagger.io/v2/swagger.json"
 dom_id: "#swagger-ui"
-validatorUrl: "https://online.swagger.io/validator"
-oauth2RedirectUrl: "http://localhost:3200/oauth2-redirect.html"
+validatorUrl: "https://online.swagger.io/validator"
\ No newline at end of file
diff --git a/test/e2e-cypress/tests/features/dynamic-default-oauth.js b/test/e2e-cypress/tests/features/dynamic-default-oauth.js
new file mode 100644
index 00000000..ad39a914
--- /dev/null
+++ b/test/e2e-cypress/tests/features/dynamic-default-oauth.js
@@ -0,0 +1,10 @@
+describe("dynamic default oauth2RedirectUrl", () => {
+  it("should render the OAS3 badge correctly", () => {
+    // This is a sanity check to make sure the badge is present.
+    // If this is failing, it's probably not related to #4865.
+    cy.visit("/")
+      .window()
+      .then(win => win.ui.getConfigs())
+      .should("include", { oauth2RedirectUrl: "http://localhost:3230/oauth2-redirect.html" })
+  })
+})