diff --git a/modules/prebidServerBidAdapter/index.js b/modules/prebidServerBidAdapter/index.js
index 5794dc86f3a..96986ed185c 100644
--- a/modules/prebidServerBidAdapter/index.js
+++ b/modules/prebidServerBidAdapter/index.js
@@ -269,11 +269,17 @@ function _appendSiteAppDevice(request, pageUrl) {
     request.app.publisher = {id: _s2sConfig.accountId}
   } else {
     request.site = {};
-    if (typeof config.getConfig('site') === 'object') {
+    if (utils.isPlainObject(config.getConfig('site'))) {
       request.site = config.getConfig('site');
     }
-    utils.deepSetValue(request.site, 'publisher.id', _s2sConfig.accountId);
-    request.site.page = pageUrl;
+    // set publisher.id if not already defined
+    if (!utils.deepAccess(request.site, 'publisher.id')) {
+      utils.deepSetValue(request.site, 'publisher.id', _s2sConfig.accountId);
+    }
+    // set site.page if not already defined
+    if (!request.site.page) {
+      request.site.page = pageUrl;
+    }
   }
   if (typeof config.getConfig('device') === 'object') {
     request.device = config.getConfig('device');
diff --git a/test/spec/modules/prebidServerBidAdapter_spec.js b/test/spec/modules/prebidServerBidAdapter_spec.js
index f66c87582f5..b4544a2ec48 100644
--- a/test/spec/modules/prebidServerBidAdapter_spec.js
+++ b/test/spec/modules/prebidServerBidAdapter_spec.js
@@ -925,7 +925,7 @@ describe('S2S Adapter', function () {
       expect(requestBid.site.content.language).to.exist.and.to.be.a('string');
       expect(requestBid.site).to.deep.equal({
         publisher: {
-          id: '1',
+          id: '1234',
           domain: 'test.com'
         },
         content: {
@@ -1095,6 +1095,59 @@ describe('S2S Adapter', function () {
       expect(requestBid.imp[0].ext.appnexus.key).to.be.equal('value')
     });
 
+    describe('config site value is added to the oRTB request', function () {
+      const s2sConfig = Object.assign({}, CONFIG, {
+        endpoint: 'https://prebid.adnxs.com/pbs/v1/openrtb2/auction',
+        adapterOptions: {
+          appnexus: {
+            key: 'value'
+          }
+        }
+      });
+      const device = {
+        ua: 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36',
+        ip: '75.97.0.47'
+      };
+
+      it('and overrides publisher and page', function () {
+        config.setConfig({
+          s2sConfig: s2sConfig,
+          site: {
+            domain: 'nytimes.com',
+            page: 'http://www.nytimes.com',
+            publisher: { id: '2' }
+          },
+          device: device
+        });
+        adapter.callBids(REQUEST, BID_REQUESTS, addBidResponse, done, ajax);
+        const requestBid = JSON.parse(server.requests[0].requestBody);
+
+        expect(requestBid.site).to.exist.and.to.be.a('object');
+        expect(requestBid.site.domain).to.equal('nytimes.com');
+        expect(requestBid.site.page).to.equal('http://www.nytimes.com');
+        expect(requestBid.site.publisher).to.exist.and.to.be.a('object');
+        expect(requestBid.site.publisher.id).to.equal('2');
+      });
+
+      it('and merges domain and page with the config site value', function () {
+        config.setConfig({
+          s2sConfig: s2sConfig,
+          site: {
+            foo: 'bar'
+          },
+          device: device
+        });
+        adapter.callBids(REQUEST, BID_REQUESTS, addBidResponse, done, ajax);
+
+        const requestBid = JSON.parse(server.requests[0].requestBody);
+        expect(requestBid.site).to.exist.and.to.be.a('object');
+        expect(requestBid.site.foo).to.equal('bar');
+        expect(requestBid.site.page).to.equal('http://mytestpage.com');
+        expect(requestBid.site.publisher).to.exist.and.to.be.a('object');
+        expect(requestBid.site.publisher.id).to.equal('1');
+      });
+    });
+
     it('when userId is defined on bids, it\'s properties should be copied to user.ext.tpid properties', function () {
       let ortb2Config = utils.deepClone(CONFIG);
       ortb2Config.endpoint = 'https://prebid.adnxs.com/pbs/v1/openrtb2/auction';