diff --git a/modules/prebidServerBidAdapter.js b/modules/prebidServerBidAdapter.js
index ebb630ceb7a..40238a766fb 100644
--- a/modules/prebidServerBidAdapter.js
+++ b/modules/prebidServerBidAdapter.js
@@ -266,6 +266,20 @@ function _appendSiteAppDevice(request) {
   }
 }
 
+function transformHeightWidth(adUnit) {
+  let sizesObj = [];
+  let sizes = utils.parseSizesInput(adUnit.sizes);
+  sizes.forEach(size => {
+    let heightWidth = size.split('x');
+    let sizeObj = {
+      'w': parseInt(heightWidth[0]),
+      'h': parseInt(heightWidth[1])
+    };
+    sizesObj.push(sizeObj);
+  });
+  return sizesObj;
+}
+
 /*
  * Protocol spec for legacy endpoint
  * e.g., https://<prebid-server-url>/v1/auction
@@ -275,6 +289,7 @@ const LEGACY_PROTOCOL = {
   buildRequest(s2sBidRequest, adUnits) {
     // pbs expects an ad_unit.video attribute if the imp is video
     adUnits.forEach(adUnit => {
+      adUnit.sizes = transformHeightWidth(adUnit);
       const videoMediaType = utils.deepAccess(adUnit, 'mediaTypes.video');
       if (videoMediaType) {
         adUnit.video = Object.assign({}, videoMediaType);
diff --git a/src/adaptermanager.js b/src/adaptermanager.js
index 6ff2387cca2..fc045f02adb 100644
--- a/src/adaptermanager.js
+++ b/src/adaptermanager.js
@@ -94,27 +94,11 @@ function getBids({bidderCode, auctionId, bidderRequestId, adUnits, labels}) {
   }, []).reduce(flatten, []).filter(val => val !== '');
 }
 
-function transformHeightWidth(adUnit) {
-  let sizesObj = [];
-  let sizes = utils.parseSizesInput(adUnit.sizes);
-  sizes.forEach(size => {
-    let heightWidth = size.split('x');
-    let sizeObj = {
-      'w': parseInt(heightWidth[0]),
-      'h': parseInt(heightWidth[1])
-    };
-    sizesObj.push(sizeObj);
-  });
-  return sizesObj;
-}
-
 function getAdUnitCopyForPrebidServer(adUnits) {
   let adaptersServerSide = _s2sConfig.bidders;
   let adUnitsCopy = utils.deepClone(adUnits);
 
   adUnitsCopy.forEach((adUnit) => {
-    adUnit.sizes = transformHeightWidth(adUnit);
-
     // filter out client side bids
     adUnit.bids = adUnit.bids.filter((bid) => {
       return includes(adaptersServerSide, bid.bidder) && (!doingS2STesting() || bid.finalSource !== s2sTestingModule.CLIENT);
@@ -281,6 +265,17 @@ exports.callBids = (adUnits, bidRequests, addBidResponse, doneCb) => {
     const s2sAdapter = _bidderRegistry[_s2sConfig.adapter];
     let tid = serverBidRequests[0].tid;
     let adUnitsS2SCopy = serverBidRequests[0].adUnitsS2SCopy;
+    adUnitsS2SCopy.forEach((adUnitCopy) => {
+      let validBids = adUnitCopy.bids.filter((bid) => {
+        return serverBidRequests.find(request => {
+          return request.bidderCode === bid.bidder &&
+          request.bids.find((reqBid) => reqBid.adUnitCode === adUnitCopy.code);
+        });
+      });
+      adUnitCopy.bids = validBids;
+    });
+
+    adUnitsS2SCopy = adUnitsS2SCopy.filter(adUnitCopy => adUnitCopy.bids.length > 0);
 
     if (s2sAdapter) {
       let s2sBidRequest = {tid, 'ad_units': adUnitsS2SCopy};
diff --git a/test/spec/modules/prebidServerBidAdapter_spec.js b/test/spec/modules/prebidServerBidAdapter_spec.js
index 383c599a133..f7f076a9100 100644
--- a/test/spec/modules/prebidServerBidAdapter_spec.js
+++ b/test/spec/modules/prebidServerBidAdapter_spec.js
@@ -27,16 +27,7 @@ const REQUEST = {
   'ad_units': [
     {
       'code': 'div-gpt-ad-1460505748561-0',
-      'sizes': [
-        {
-          'w': 300,
-          'h': 250
-        },
-        {
-          'w': 300,
-          'h': 600
-        }
-      ],
+      'sizes': [[300, 250], [300, 600]],
       'mediaTypes': {
         'banner': {
           'sizes': [[ 300, 250 ], [ 300, 300 ]]
@@ -68,7 +59,7 @@ const VIDEO_REQUEST = {
   'ad_units': [
     {
       'code': 'div-gpt-ad-1460505748561-0',
-      'sizes': [{ 'w': 640, 'h': 480 }],
+      'sizes': [640, 480],
       'mediaTypes': {
         'video': {
           'playerSize': [[ 640, 480 ]],
@@ -103,12 +94,7 @@ const BID_REQUESTS = [
         'bid_id': '123',
         'adUnitCode': 'div-gpt-ad-1460505748561-0',
         'transactionId': '4ef956ad-fd83-406d-bd35-e4bb786ab86c',
-        'sizes': [
-          {
-            'w': 300,
-            'h': 250
-          }
-        ],
+        'sizes': [300, 250],
         'bidId': '259fb43aaa06c1',
         'bidderRequestId': '3d1063078dfcc8',
         'auctionId': '173afb6d132ba3'