diff --git a/modules/33acrossBidAdapter.js b/modules/33acrossBidAdapter.js
index 497cf9f7110..2ecab4013f9 100644
--- a/modules/33acrossBidAdapter.js
+++ b/modules/33acrossBidAdapter.js
@@ -83,6 +83,14 @@ function _createServerRequest(bidRequest, gdprConsent) {
       gdpr: (gdprConsent.gdprApplies === true) ? 1 : 0
     }
   };
+  ttxRequest.ext = {
+    ttx: {
+      caller: [{
+        'name': 'prebidjs',
+        'version': '$prebid.version$'
+      }]
+    }
+  }
 
   // Finally, set the openRTB 'test' param if this is to be a test bid
   if (params.test === 1) {
diff --git a/test/spec/modules/33acrossBidAdapter_spec.js b/test/spec/modules/33acrossBidAdapter_spec.js
index c8f0421e1e6..1fc77a7e14d 100644
--- a/test/spec/modules/33acrossBidAdapter_spec.js
+++ b/test/spec/modules/33acrossBidAdapter_spec.js
@@ -58,6 +58,14 @@ describe('33acrossBidAdapter:', function () {
         ext: {
           gdpr: 0
         }
+      },
+      ext: {
+        ttx: {
+          caller: [{
+            'name': 'prebidjs',
+            'version': '$prebid.version$'
+          }]
+        }
       }
     };