diff --git a/modules/proxistoreBidAdapter.js b/modules/proxistoreBidAdapter.js
index a399a906402..6facf5d1480 100644
--- a/modules/proxistoreBidAdapter.js
+++ b/modules/proxistoreBidAdapter.js
@@ -9,7 +9,6 @@ function _mapSizes(sizes) {
 
 function _createServerRequest(bidRequests, bidderRequest) {
   const payload = {
-    bidId: bidRequests.map(req => req.bidId),
     auctionId: bidRequests[0].auctionId,
     transactionId: bidRequests[0].transactionId,
     sizes: _mapSizes(bidRequests.map(x => x.sizes)),
@@ -20,6 +19,9 @@ function _createServerRequest(bidRequests, bidderRequest) {
     }
   };
 
+  const bidIds = bidRequests.map(req => req.bidId);
+  bidIds.length === 1 ? payload.bidId = bidIds[0] : payload.bidIds = bidIds;
+
   const options = {
     contentType: 'application/json',
     withCredentials: true
diff --git a/test/spec/modules/proxistoreBidAdapter_spec.js b/test/spec/modules/proxistoreBidAdapter_spec.js
index 4fd7d97ae99..579ef5fdb3b 100644
--- a/test/spec/modules/proxistoreBidAdapter_spec.js
+++ b/test/spec/modules/proxistoreBidAdapter_spec.js
@@ -50,10 +50,15 @@ describe('ProxistoreBidAdapter', function () {
     });
     it('should have the value consentGiven to true bc we have 418 in the vendor list', function () {
       const data = JSON.parse(request.data);
+
       expect(data.gdpr.consentString).equal(bidderRequest.gdprConsent.consentString);
       expect(data.gdpr.applies).to.be.true;
       expect(data.gdpr.consentGiven).to.be.true;
     });
+    it('should have a property bidId if there is only one bid', function () {
+      const data = JSON.parse(request.data);
+      expect(data.hasOwnProperty('bidId')).to.be.true;
+    })
   });
 
   describe('interpretResponse', function () {