diff --git a/modules/gumgumBidAdapter.js b/modules/gumgumBidAdapter.js
index 60f446b12ee..585d3279a07 100644
--- a/modules/gumgumBidAdapter.js
+++ b/modules/gumgumBidAdapter.js
@@ -41,7 +41,7 @@ function _getBrowserParams(topWindowUrl) {
   try {
     topWindow = global.top;
     topScreen = topWindow.screen;
-    topUrl = topWindowUrl || utils.getTopWindowUrl();
+    topUrl = topWindowUrl || '';
   } catch (error) {
     utils.logError(error);
     return browserParams
@@ -145,6 +145,7 @@ function buildRequests (validBidRequests, bidderRequest) {
       userId = {}
     } = bidRequest;
     const data = {};
+    const sizes = bidRequest.mediaTypes && bidRequest.mediaTypes.banner && bidRequest.mediaTypes.banner.sizes;
     const topWindowUrl = bidderRequest && bidderRequest.refererInfo && bidderRequest.refererInfo.referer;
     if (pageViewId) {
       data.pv = pageViewId
@@ -177,7 +178,7 @@ function buildRequests (validBidRequests, bidderRequest) {
       tId: transactionId,
       pi: data.pi,
       selector: params.selector,
-      sizes: bidRequest.sizes || bidRequest.mediatype[banner].sizes,
+      sizes: sizes || bidRequest.sizes,
       url: BID_ENDPOINT,
       method: 'GET',
       data: Object.assign(data, _getBrowserParams(topWindowUrl), _getDigiTrustQueryParams(userId), _getTradeDeskIDParam(userId))
diff --git a/test/spec/modules/gumgumBidAdapter_spec.js b/test/spec/modules/gumgumBidAdapter_spec.js
index 82c8e494533..0d00eb2b93c 100644
--- a/test/spec/modules/gumgumBidAdapter_spec.js
+++ b/test/spec/modules/gumgumBidAdapter_spec.js
@@ -21,7 +21,11 @@ describe('gumgumAdapter', function () {
         'bidfloor': 0.05
       },
       'adUnitCode': 'adunit-code',
-      'sizes': [[300, 250], [300, 600], [1, 1]],
+      'mediaTypes': {
+        'banner': {
+          sizes: [[300, 250], [300, 600], [1, 1]]
+        }
+      },
       'bidId': '30b31c1838de1e',
       'bidderRequestId': '22edbae2733bf6',
       'auctionId': '1d1a030790a475',