diff --git a/modules/gumgumBidAdapter.js b/modules/gumgumBidAdapter.js
index 3a347163e6d..d071127f6b7 100644
--- a/modules/gumgumBidAdapter.js
+++ b/modules/gumgumBidAdapter.js
@@ -60,7 +60,7 @@ function _getBrowserParams(topWindowUrl) {
     pu: topUrl,
     ce: storage.cookiesAreEnabled(),
     dpr: topWindow.devicePixelRatio || 1,
-    jcsi: JSON.stringify({ t: 0, rq: 8 }),
+    jcsi: encodeURIComponent(JSON.stringify({ t: 0, rq: 8 })),
     ogu: getOgURL()
   }
 
diff --git a/test/spec/modules/gumgumBidAdapter_spec.js b/test/spec/modules/gumgumBidAdapter_spec.js
index 9073ad3bfda..a2fbc2cf029 100644
--- a/test/spec/modules/gumgumBidAdapter_spec.js
+++ b/test/spec/modules/gumgumBidAdapter_spec.js
@@ -228,6 +228,13 @@ describe('gumgumAdapter', function () {
         expect(bidRequest.data).to.not.include.any.keys('ns');
       }
     });
+    it('has jcsi param correctly encoded', function () {
+      const jcsi = JSON.stringify({ t: 0, rq: 8 });
+      const encodedJCSI = encodeURIComponent(jcsi);
+      const bidRequest = spec.buildRequests(bidRequests)[0];
+      expect(bidRequest.data.jcsi).to.not.contain(/\{.*\}/);
+      expect(bidRequest.data.jcsi).to.eq(encodedJCSI);
+    });
   })
 
   describe('interpretResponse', function () {