diff --git a/CHANGELOG.md b/CHANGELOG.md
index c7be42e..1d9ed33 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,7 +7,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 ## [Unreleased]
 
 ### Added
+- Added `defaultProtocol` configuration option as fallback if no config is provided.
 ### Changed
+- set `odata` as the service protocol if no protocol is set to match the default behavior of `@sap/cds`. Provide `cds.env.openapi.defaultProtocol = "rest"` to restore old behavior.
 ### Deprecated
 ### Removed
 ### Fixed
diff --git a/lib/compile/index.js b/lib/compile/index.js
index 1bfb40f..09753f3 100644
--- a/lib/compile/index.js
+++ b/lib/compile/index.js
@@ -51,7 +51,7 @@ function processor(csn, options = {}) {
   }
     const openApiOptions = toOpenApiOptions(csdl, csn, options);
     const serviceName = csdl.$EntityContainer.replace(/\.[^.]+$/, "");
-    openApiDocs = _getOpenApi(csdl, openApiOptions,serviceName);
+    openApiDocs = _getOpenApi(csdl, openApiOptions, serviceName);
     return Object.keys(openApiDocs).length === 1
       ? openApiDocs[serviceName]
       : _iterate(openApiDocs);
@@ -118,11 +118,12 @@ function toOpenApiOptions(csdl, csn, options = {}) {
   }
 
   const envOptions = cds.env.openapi instanceof Object && !Array.isArray(cds.env.openapi) ? cds.env.openapi : {};
+  envOptions.defaultProtocol = envOptions.defaultProtocol ?? "odata";
   const fileOptions = _readConfigFile(callerOptions["config-file"]);
   const result = { ...envOptions, ...fileOptions, ...callerOptions };
   delete result["config-file"];
 
-  const protocols = _getProtocols(csdl, csn, result.odataVersion);
+  const protocols = _getProtocols(csdl, csn, result.odataVersion, result.defaultProtocol);
 
   if (result.url) {
     const servicePaths = _servicePath(csdl, csn, protocols);
@@ -143,20 +144,20 @@ function toOpenApiOptions(csdl, csn, options = {}) {
   return result;
 }
 
-function _getProtocols(csdl, csn, odataVersion) {
+function _getProtocols(csdl, csn, odataVersion, defaultProtocol) {
   if (csdl.$EntityContainer) {
     const serviceName = csdl.$EntityContainer.replace(/\.[^.]+$/, "");
     const service = csn.definitions[serviceName];
     const protocols = [];
 
     if(odataVersion === "4.01"){
-      protocols.push("rest");
+      protocols.push("odata");
     }
     else if(odataVersion === "4.0"){
       protocols.push("odata");
     }
     else if (!service["@protocol"]) {
-      protocols.push("rest"); //taking rest as default in case no relevant protocol is there
+      protocols.push(defaultProtocol); // matches cds's default protocol when none is annotated
     } else if (service["@protocol"] === "none") {
       // if @protocol is 'none' then throw an error
       throw new Error(
diff --git a/test/lib/compile/openapi.test.js b/test/lib/compile/openapi.test.js
index 79e5374..a74f7be 100644
--- a/test/lib/compile/openapi.test.js
+++ b/test/lib/compile/openapi.test.js
@@ -262,6 +262,36 @@ service CatalogService {
     assert(openapi.servers[0].url.includes('odata'));
   });
 
+  test('default service without @protocol renders server URL with odata/v4', () => {
+    const csn = cds.compile.to.csn(`
+      @path: 'catalog'
+      service CatalogService {
+        entity Books {
+          key ID : Integer;
+          title   : String;
+        }
+      }`
+    );
+    const openapi = toOpenApi(csn);
+    assert(openapi.servers[0].url.includes('odata/v4'));
+    assert(!openapi.servers[0].url.includes('rest'));
+  });
+
+  test('defaultProtocol overrides OData for a service without @protocol', () => {
+    const csn = cds.compile.to.csn(`
+      @path: 'catalog'
+      service CatalogService {
+        entity Books {
+          key ID : Integer;
+          title   : String;
+        }
+      }`
+    );
+    const openapi = toOpenApi(csn, { 'openapi:defaultProtocol': 'rest' });
+    assert(openapi.servers[0].url.includes('rest/catalog'));
+    assert(!openapi.servers[0].url.includes('odata'));
+  });
+
   test('options: Multiple servers', () => {
     const csn = cds.compile.to.csn(`
       service A {entity E { key ID : UUID; };};`