diff --git a/modules/prebidServerBidAdapter/index.js b/modules/prebidServerBidAdapter/index.js
index a7a3199675d..0ff967f1da9 100644
--- a/modules/prebidServerBidAdapter/index.js
+++ b/modules/prebidServerBidAdapter/index.js
@@ -504,6 +504,9 @@ const OPEN_RTB_PROTOCOL = {
           // Don't push oustream w/o renderer to request object.
           utils.logError('Outstream bid without renderer cannot be sent to Prebid Server.');
         } else {
+          if (videoParams.context === 'instream' && !videoParams.hasOwnProperty('placement')) {
+            videoParams.placement = 1;
+          }
           mediaTypes['video'] = videoParams;
         }
       }
diff --git a/test/spec/modules/prebidServerBidAdapter_spec.js b/test/spec/modules/prebidServerBidAdapter_spec.js
index a300a10d31b..d29657e8e53 100644
--- a/test/spec/modules/prebidServerBidAdapter_spec.js
+++ b/test/spec/modules/prebidServerBidAdapter_spec.js
@@ -509,6 +509,22 @@ describe('S2S Adapter', function () {
       expect(requestBid.imp[0].video).to.not.exist;
     });
 
+    it('should default video placement if not defined and instream', function () {
+      let ortb2Config = utils.deepClone(CONFIG);
+      ortb2Config.endpoint = 'https://prebid.adnxs.com/pbs/v1/openrtb2/auction';
+
+      config.setConfig({ s2sConfig: ortb2Config });
+
+      let videoBid = utils.deepClone(VIDEO_REQUEST);
+      videoBid.ad_units[0].mediaTypes.video.context = 'instream';
+      adapter.callBids(videoBid, BID_REQUESTS, addBidResponse, done, ajax);
+
+      const requestBid = JSON.parse(server.requests[0].requestBody);
+      expect(requestBid.imp[0].banner).to.not.exist;
+      expect(requestBid.imp[0].video).to.exist;
+      expect(requestBid.imp[0].video.placement).to.equal(1);
+    });
+
     it('exists and is a function', function () {
       expect(adapter.callBids).to.exist.and.to.be.a('function');
     });