diff --git a/src/prebid.js b/src/prebid.js
index 1710849ba92..f3ea64d1e83 100644
--- a/src/prebid.js
+++ b/src/prebid.js
@@ -83,50 +83,58 @@ function validateSizes(sizes, targLength) {
 }
 
 function validateBannerMediaType(adUnit) {
-  const banner = adUnit.mediaTypes.banner;
+  const validatedAdUnit = utils.deepClone(adUnit);
+  const banner = validatedAdUnit.mediaTypes.banner;
   const bannerSizes = validateSizes(banner.sizes);
   if (bannerSizes.length > 0) {
     banner.sizes = bannerSizes;
     // Deprecation Warning: This property will be deprecated in next release in favor of adUnit.mediaTypes.banner.sizes
-    adUnit.sizes = bannerSizes;
+    validatedAdUnit.sizes = bannerSizes;
   } else {
     utils.logError('Detected a mediaTypes.banner object without a proper sizes field.  Please ensure the sizes are listed like: [[300, 250], ...].  Removing invalid mediaTypes.banner object from request.');
-    delete adUnit.mediaTypes.banner
+    delete validatedAdUnit.mediaTypes.banner
   }
+  return validatedAdUnit;
 }
 
 function validateVideoMediaType(adUnit) {
-  const video = adUnit.mediaTypes.video;
-  let tarPlayerSizeLen = (typeof video.playerSize[0] === 'number') ? 2 : 1;
-
-  const videoSizes = validateSizes(video.playerSize, tarPlayerSizeLen);
-  if (videoSizes.length > 0) {
-    if (tarPlayerSizeLen === 2) {
-      utils.logInfo('Transforming video.playerSize from [640,480] to [[640,480]] so it\'s in the proper format.');
+  const validatedAdUnit = utils.deepClone(adUnit);
+  const video = validatedAdUnit.mediaTypes.video;
+  if (video.playerSize) {
+    let tarPlayerSizeLen = (typeof video.playerSize[0] === 'number') ? 2 : 1;
+
+    const videoSizes = validateSizes(video.playerSize, tarPlayerSizeLen);
+    if (videoSizes.length > 0) {
+      if (tarPlayerSizeLen === 2) {
+        utils.logInfo('Transforming video.playerSize from [640,480] to [[640,480]] so it\'s in the proper format.');
+      }
+      video.playerSize = videoSizes;
+      // Deprecation Warning: This property will be deprecated in next release in favor of adUnit.mediaTypes.video.playerSize
+      validatedAdUnit.sizes = videoSizes;
+    } else {
+      utils.logError('Detected incorrect configuration of mediaTypes.video.playerSize.  Please specify only one set of dimensions in a format like: [[640, 480]]. Removing invalid mediaTypes.video.playerSize property from request.');
+      delete validatedAdUnit.mediaTypes.video.playerSize;
     }
-    video.playerSize = videoSizes;
-    // Deprecation Warning: This property will be deprecated in next release in favor of adUnit.mediaTypes.video.playerSize
-    adUnit.sizes = videoSizes;
-  } else {
-    utils.logError('Detected incorrect configuration of mediaTypes.video.playerSize.  Please specify only one set of dimensions in a format like: [[640, 480]]. Removing invalid mediaTypes.video.playerSize property from request.');
-    delete adUnit.mediaTypes.video.playerSize;
   }
+  return validatedAdUnit;
 }
 
 function validateNativeMediaType(adUnit) {
-  const native = adUnit.mediaTypes.native;
+  const validatedAdUnit = utils.deepClone(adUnit);
+  const native = validatedAdUnit.mediaTypes.native;
   if (native.image && native.image.sizes && !Array.isArray(native.image.sizes)) {
     utils.logError('Please use an array of sizes for native.image.sizes field.  Removing invalid mediaTypes.native.image.sizes property from request.');
-    delete adUnit.mediaTypes.native.image.sizes;
+    delete validatedAdUnit.mediaTypes.native.image.sizes;
   }
   if (native.image && native.image.aspect_ratios && !Array.isArray(native.image.aspect_ratios)) {
     utils.logError('Please use an array of sizes for native.image.aspect_ratios field.  Removing invalid mediaTypes.native.image.aspect_ratios property from request.');
-    delete adUnit.mediaTypes.native.image.aspect_ratios;
+    delete validatedAdUnit.mediaTypes.native.image.aspect_ratios;
   }
   if (native.icon && native.icon.sizes && !Array.isArray(native.icon.sizes)) {
     utils.logError('Please use an array of sizes for native.icon.sizes field.  Removing invalid mediaTypes.native.icon.sizes property from request.');
-    delete adUnit.mediaTypes.native.icon.sizes;
+    delete validatedAdUnit.mediaTypes.native.icon.sizes;
   }
+  return validatedAdUnit;
 }
 
 export const adUnitSetupChecks = {
@@ -137,29 +145,34 @@ export const adUnitSetupChecks = {
 };
 
 export const checkAdUnitSetup = hook('sync', function (adUnits) {
-  return adUnits.filter(adUnit => {
+  const validatedAdUnits = [];
+
+  adUnits.forEach(adUnit => {
     const mediaTypes = adUnit.mediaTypes;
+    let validatedBanner, validatedVideo, validatedNative;
     if (!mediaTypes || Object.keys(mediaTypes).length === 0) {
       utils.logError(`Detected adUnit.code '${adUnit.code}' did not have a 'mediaTypes' object defined.  This is a required field for the auction, so this adUnit has been removed.`);
-      return false;
+      return;
     }
 
     if (mediaTypes.banner) {
-      validateBannerMediaType(adUnit);
+      validatedBanner = validateBannerMediaType(adUnit);
     }
 
     if (mediaTypes.video) {
-      const video = mediaTypes.video;
-      if (video.playerSize) {
-        validateVideoMediaType(adUnit);
-      }
+      validatedVideo = validatedBanner ? validateVideoMediaType(validatedBanner) : validateVideoMediaType(adUnit);
     }
 
     if (mediaTypes.native) {
-      validateNativeMediaType(adUnit);
+      validatedNative = validatedVideo ? validateNativeMediaType(validatedVideo) : validatedBanner ? validateNativeMediaType(validatedBanner) : validateNativeMediaType(adUnit);
     }
-    return true;
+
+    const validatedAdUnit = Object.assign({}, validatedBanner, validatedVideo, validatedNative);
+
+    validatedAdUnits.push(validatedAdUnit);
   });
+
+  return validatedAdUnits;
 }, 'checkAdUnitSetup');
 
 /// ///////////////////////////////
@@ -192,7 +205,7 @@ $$PREBID_GLOBAL$$.getAdserverTargetingForAdUnitCodeStr = function (adunitCode) {
  * @alias module:pbjs.getAdserverTargetingForAdUnitCode
  * @returns {Object}  returnObj return bids
  */
-$$PREBID_GLOBAL$$.getAdserverTargetingForAdUnitCode = function(adUnitCode) {
+$$PREBID_GLOBAL$$.getAdserverTargetingForAdUnitCode = function (adUnitCode) {
   return $$PREBID_GLOBAL$$.getAdserverTargeting(adUnitCode)[adUnitCode];
 };
 
@@ -300,7 +313,7 @@ $$PREBID_GLOBAL$$.setTargetingForGPTAsync = function (adUnit, customSlotMatching
  * @param  {(string|string[])} adUnitCode adUnitCode or array of adUnitCodes
  * @alias module:pbjs.setTargetingForAst
  */
-$$PREBID_GLOBAL$$.setTargetingForAst = function(adUnitCodes) {
+$$PREBID_GLOBAL$$.setTargetingForAst = function (adUnitCodes) {
   utils.logInfo('Invoking $$PREBID_GLOBAL$$.setTargetingForAn', arguments);
   if (!targeting.isApntagDefined()) {
     utils.logError('window.apntag is not defined on the page');
@@ -448,6 +461,8 @@ $$PREBID_GLOBAL$$.requestBids = hook('async', function ({ bidsBackHandler, timeo
 
   utils.logInfo('Invoking $$PREBID_GLOBAL$$.requestBids', arguments);
 
+  adUnits = checkAdUnitSetup(adUnits);
+
   if (adUnitCodes && adUnitCodes.length) {
     // if specific adUnitCodes supplied filter adUnits for those codes
     adUnits = adUnits.filter(unit => includes(adUnitCodes, unit.code));
@@ -456,8 +471,6 @@ $$PREBID_GLOBAL$$.requestBids = hook('async', function ({ bidsBackHandler, timeo
     adUnitCodes = adUnits && adUnits.map(unit => unit.code);
   }
 
-  adUnits = checkAdUnitSetup(adUnits);
-
   /*
    * for a given adunit which supports a set of mediaTypes
    * and a given bidder which supports a set of mediaTypes
@@ -466,7 +479,7 @@ $$PREBID_GLOBAL$$.requestBids = hook('async', function ({ bidsBackHandler, timeo
    */
   adUnits.forEach(adUnit => {
     // get the adunit's mediaTypes, defaulting to banner if mediaTypes isn't present
-    const adUnitMediaTypes = Object.keys(adUnit.mediaTypes || {'banner': 'banner'});
+    const adUnitMediaTypes = Object.keys(adUnit.mediaTypes || { 'banner': 'banner' });
 
     // get the bidder's mediaTypes
     const allBidders = adUnit.bids.map(bid => bid.bidder);
@@ -512,7 +525,7 @@ $$PREBID_GLOBAL$$.requestBids = hook('async', function ({ bidsBackHandler, timeo
     return;
   }
 
-  const auction = auctionManager.createAuction({adUnits, adUnitCodes, callback: bidsBackHandler, cbTimeout, labels, auctionId});
+  const auction = auctionManager.createAuction({ adUnits, adUnitCodes, callback: bidsBackHandler, cbTimeout, labels, auctionId });
 
   let adUnitsLen = adUnits.length;
   if (adUnitsLen > 15) {
@@ -843,7 +856,7 @@ $$PREBID_GLOBAL$$.que.push(() => listenMessagesFromCreative());
  *                            the Prebid script has been fully loaded.
  * @alias module:pbjs.cmd.push
  */
-$$PREBID_GLOBAL$$.cmd.push = function(command) {
+$$PREBID_GLOBAL$$.cmd.push = function (command) {
   if (typeof command === 'function') {
     try {
       command.call();
@@ -858,7 +871,7 @@ $$PREBID_GLOBAL$$.cmd.push = function(command) {
 $$PREBID_GLOBAL$$.que.push = $$PREBID_GLOBAL$$.cmd.push;
 
 function processQueue(queue) {
-  queue.forEach(function(cmd) {
+  queue.forEach(function (cmd) {
     if (typeof cmd.called === 'undefined') {
       try {
         cmd.call();
@@ -873,7 +886,7 @@ function processQueue(queue) {
 /**
  * @alias module:pbjs.processQueue
  */
-$$PREBID_GLOBAL$$.processQueue = function() {
+$$PREBID_GLOBAL$$.processQueue = function () {
   hook.ready();
   processQueue($$PREBID_GLOBAL$$.que);
   processQueue($$PREBID_GLOBAL$$.cmd);
diff --git a/test/spec/unit/pbjs_api_spec.js b/test/spec/unit/pbjs_api_spec.js
index 8a142d7a6aa..960ccf08c92 100644
--- a/test/spec/unit/pbjs_api_spec.js
+++ b/test/spec/unit/pbjs_api_spec.js
@@ -1770,8 +1770,6 @@ describe('Unit: Prebid Module', function () {
     });
 
     describe('multiformat requests', function () {
-      let spyCallBids;
-      let createAuctionStub;
       let adUnits;
 
       beforeEach(function () {
@@ -1791,14 +1789,10 @@ describe('Unit: Prebid Module', function () {
         }];
         adUnitCodes = ['adUnit-code'];
         configObj.setConfig({maxRequestsPerOrigin: Number.MAX_SAFE_INTEGER || 99999999});
-        let auction = auctionModule.newAuction({adUnits, adUnitCodes, callback: function() {}, cbTimeout: timeout});
-        spyCallBids = sinon.spy(adapterManager, 'callBids');
-        createAuctionStub = sinon.stub(auctionModule, 'newAuction');
-        createAuctionStub.returns(auction);
+        sinon.spy(adapterManager, 'callBids');
       })
 
       afterEach(function () {
-        auctionModule.newAuction.restore();
         adapterManager.callBids.restore();
       });
 
@@ -1821,7 +1815,6 @@ describe('Unit: Prebid Module', function () {
 
         const spyArgs = adapterManager.callBids.getCall(0);
         const biddersCalled = spyArgs.args[0][0].bids;
-
         // only appnexus supports native
         expect(biddersCalled.length).to.equal(1);
       });