diff --git a/src/node/hooks/express/openapi.ts b/src/node/hooks/express/openapi.ts
index 3b7dd450904..926ae34f234 100644
--- a/src/node/hooks/express/openapi.ts
+++ b/src/node/hooks/express/openapi.ts
@@ -868,8 +868,9 @@ const getApiRootForVersion = (version:string, style:any = APIPathStyle.FLAT): st
 const generateServerForApiVersion = (apiRoot:string, req:any): {
   url:string
 } => ({
-  url: `${settings.ssl ? 'https' : 'http'}://${req.headers.host}${apiRoot}`,
+  url: `${req.protocol}://${req.headers.host}${apiRoot}`,
 });
 
 exports.generateDefinitionForVersion = generateDefinitionForVersion;
 exports.APIPathStyle = APIPathStyle;
+exports.generateServerForApiVersion = generateServerForApiVersion;
diff --git a/src/tests/backend/specs/openapi.ts b/src/tests/backend/specs/openapi.ts
new file mode 100644
index 00000000000..1b49e9c31ab
--- /dev/null
+++ b/src/tests/backend/specs/openapi.ts
@@ -0,0 +1,25 @@
+'use strict';
+
+const assert = require('assert').strict;
+
+describe('openapi server URL generation', function () {
+  let generateServerForApiVersion: (apiRoot: string, req: any) => {url: string};
+
+  before(function () {
+    ({generateServerForApiVersion} = require('../../../node/hooks/express/openapi'));
+  });
+
+  const mockReq = (protocol: string, host: string) => ({protocol, headers: {host}});
+
+  it('emits http:// for a plain HTTP request', function () {
+    assert.deepEqual(
+        generateServerForApiVersion('/api/1.2.15', mockReq('http', 'pad.example.com')),
+        {url: 'http://pad.example.com/api/1.2.15'});
+  });
+
+  it('emits https:// when the request protocol is https (TLS or reverse proxy)', function () {
+    assert.deepEqual(
+        generateServerForApiVersion('/api/1.2.15', mockReq('https', 'pad.example.com')),
+        {url: 'https://pad.example.com/api/1.2.15'});
+  });
+});