diff --git a/modules/improvedigitalBidAdapter.js b/modules/improvedigitalBidAdapter.js
index 4ee2226395b..cd7ab1bd50b 100644
--- a/modules/improvedigitalBidAdapter.js
+++ b/modules/improvedigitalBidAdapter.js
@@ -6,7 +6,7 @@ import { BANNER, NATIVE, VIDEO } from '../src/mediaTypes';
 const BIDDER_CODE = 'improvedigital';
 
 export const spec = {
-  version: '6.0.0',
+  version: '6.0.1',
   code: BIDDER_CODE,
   aliases: ['id'],
   supportedMediaTypes: [BANNER, NATIVE, VIDEO],
@@ -170,6 +170,12 @@ export const spec = {
   }
 };
 
+function isInstreamVideo(bid) {
+  const videoMediaType = utils.deepAccess(bid, 'mediaTypes.video');
+  const context = utils.deepAccess(bid, 'mediaTypes.video.context');
+  return bid.mediaType === 'video' || (videoMediaType && context !== 'outstream');
+}
+
 function getNormalizedBidRequest(bid) {
   let adUnitId = utils.getBidIdParameter('adUnitCode', bid) || null;
   let placementId = utils.getBidIdParameter('placementId', bid.params) || null;
@@ -189,9 +195,7 @@ function getNormalizedBidRequest(bid) {
   const bidFloorCur = utils.getBidIdParameter('bidFloorCur', bid.params);
 
   let normalizedBidRequest = {};
-  const videoMediaType = utils.deepAccess(bid, 'mediaTypes.video');
-  const context = utils.deepAccess(bid, 'mediaTypes.video.context');
-  if (bid.mediaType === 'video' || (videoMediaType && context !== 'outstream')) {
+  if (isInstreamVideo(bid)) {
     normalizedBidRequest.adTypes = [ VIDEO ];
   }
   if (placementId) {
@@ -209,7 +213,7 @@ function getNormalizedBidRequest(bid) {
     normalizedBidRequest.keyValues = keyValues;
   }
 
-  if (config.getConfig('improvedigital.usePrebidSizes') === true && bid.sizes && bid.sizes.length > 0) {
+  if (config.getConfig('improvedigital.usePrebidSizes') === true && !isInstreamVideo(bid) && bid.sizes && bid.sizes.length > 0) {
     normalizedBidRequest.format = bid.sizes;
   } else if (singleSizeFilter && singleSizeFilter.w && singleSizeFilter.h) {
     normalizedBidRequest.size = {};
diff --git a/test/spec/modules/improvedigitalBidAdapter_spec.js b/test/spec/modules/improvedigitalBidAdapter_spec.js
index 2d9d51c0d68..8ac8c8e85df 100644
--- a/test/spec/modules/improvedigitalBidAdapter_spec.js
+++ b/test/spec/modules/improvedigitalBidAdapter_spec.js
@@ -212,6 +212,22 @@ describe('Improve Digital Adapter Tests', function () {
       expect(params.bid_request.imp[0].ad_types).to.deep.equal(['video']);
     });
 
+    it('should not set Prebid sizes in bid request for instream video', function () {
+      const getConfigStub = sinon.stub(config, 'getConfig');
+      getConfigStub.withArgs('improvedigital.usePrebidSizes').returns(true);
+      const bidRequest = Object.assign({}, simpleBidRequest);
+      bidRequest.mediaTypes = {
+        video: {
+          context: 'instream',
+          playerSize: [640, 480]
+        }
+      };
+      const request = spec.buildRequests([bidRequest])[0];
+      const params = JSON.parse(decodeURIComponent(request.data.substring(PARAM_PREFIX.length)));
+      expect(params.bid_request.imp[0].banner.format).to.not.exist;
+      getConfigStub.restore();
+    });
+
     it('should not set ad type for outstream video', function() {
       const bidRequest = Object.assign({}, simpleBidRequest);
       bidRequest.mediaTypes = {