diff --git a/modules/gumgumBidAdapter.js b/modules/gumgumBidAdapter.js
index 54d845be7ad..8364cd57579 100644
--- a/modules/gumgumBidAdapter.js
+++ b/modules/gumgumBidAdapter.js
@@ -219,9 +219,15 @@ function buildRequests (validBidRequests, bidderRequest) {
       transactionId,
       userId = {}
     } = bidRequest;
-    const bannerSizes = mediaTypes.banner && mediaTypes.banner.sizes;
+    let sizes = [1, 1];
     let data = {};
 
+    if (mediaTypes.banner) {
+      sizes = mediaTypes.banner.sizes;
+    } else if (mediaTypes.video) {
+      sizes = mediaTypes.video.playerSize;
+    }
+
     if (pageViewId) {
       data.pv = pageViewId;
     }
@@ -278,7 +284,7 @@ function buildRequests (validBidRequests, bidderRequest) {
       tId: transactionId,
       pi: data.pi,
       selector: params.selector,
-      sizes: bannerSizes,
+      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 7022f8f96dd..65ec52aa8c4 100644
--- a/test/spec/modules/gumgumBidAdapter_spec.js
+++ b/test/spec/modules/gumgumBidAdapter_spec.js
@@ -114,6 +114,24 @@ describe('gumgumAdapter', function () {
         }
       }
     ];
+    const vidMediaTypes = {
+      video: {
+        playerSize: [640, 480],
+        context: 'instream',
+        minduration: 1,
+        maxduration: 2,
+        linearity: 1,
+        startdelay: 1,
+        placement: 123456,
+        protocols: [1, 2]
+      }
+    };
+
+    it('should return a defined sizes field for video', function () {
+      const request = { ...bidRequests[0], mediaTypes: vidMediaTypes, params: { 'videoPubID': 123 } };
+      const bidRequest = spec.buildRequests([request])[0];
+      expect(bidRequest.sizes).to.equal(vidMediaTypes.video.playerSize);
+    });
 
     it('sends bid request to ENDPOINT via GET', function () {
       const request = spec.buildRequests(bidRequests)[0];
@@ -145,21 +163,7 @@ describe('gumgumAdapter', function () {
       expect(bidRequest.data).to.not.include.any.keys('t');
     });
     it('should send pubId if videoPubID param is specified', function () {
-      const mediaTypes = {
-        video: {
-          playerSize: [640, 480],
-          context: 'instream',
-          minduration: 1,
-          maxduration: 2,
-          linearity: 1,
-          startdelay: 1,
-          placement: 123456,
-          protocols: [1, 2]
-        }
-      };
-      const request = Object.assign({}, bidRequests[0]);
-      request.mediaTypes = mediaTypes
-      request.params = { 'videoPubID': 123 };
+      const request = { ...bidRequests[0], mediaTypes: vidMediaTypes, params: { 'videoPubID': 123 } };
       const bidRequest = spec.buildRequests([request])[0];
       expect(bidRequest.data).to.include.any.keys('pubId');
       expect(bidRequest.data.pubId).to.equal(request.params.videoPubID);
@@ -423,7 +427,7 @@ describe('gumgumAdapter', function () {
     });
 
     it('updates jcsi object when the server response jcsi prop is found', function () {
-      const response = Object.assign({cw: 'AD_JSON'}, serverResponse);
+      const response = Object.assign({ cw: 'AD_JSON' }, serverResponse);
       const bidResponse = spec.interpretResponse({ body: response }, bidRequest)[0].ad;
       const decodedResponse = JSON.parse(atob(bidResponse));
       expect(decodedResponse.jcsi).to.eql(JCSI);