diff --git a/modules/priceFloors.js b/modules/priceFloors.js
index 3555fedbf3a..5f7a39e0784 100644
--- a/modules/priceFloors.js
+++ b/modules/priceFloors.js
@@ -64,13 +64,19 @@ function getHostNameFromReferer(referer) {
   return referrerHostname;
 }
 
+// First look into bidRequest!
+function getGptSlotFromBidRequest(bidRequest) {
+  const isGam = utils.deepAccess(bidRequest, 'ortb2Imp.ext.data.adserver.name') === 'gam';
+  return isGam && bidRequest.ortb2Imp.ext.data.adserver.adslot;
+}
+
 /**
  * @summary floor field types with their matching functions to resolve the actual matched value
  */
 export let fieldMatchingFunctions = {
   'size': (bidRequest, bidResponse) => utils.parseGPTSingleSizeArray(bidResponse.size) || '*',
   'mediaType': (bidRequest, bidResponse) => bidResponse.mediaType || 'banner',
-  'gptSlot': (bidRequest, bidResponse) => utils.getGptSlotInfoForAdUnitCode(bidRequest.adUnitCode).gptSlot,
+  'gptSlot': (bidRequest, bidResponse) => getGptSlotFromBidRequest(bidRequest) || utils.getGptSlotInfoForAdUnitCode(bidRequest.adUnitCode).gptSlot,
   'domain': (bidRequest, bidResponse) => referrerHostname || getHostNameFromReferer(getRefererInfo().referer),
   'adUnitCode': (bidRequest, bidResponse) => bidRequest.adUnitCode
 }
diff --git a/test/spec/integration/faker/googletag.js b/test/spec/integration/faker/googletag.js
index 9d91bf315d9..1d1a7512153 100644
--- a/test/spec/integration/faker/googletag.js
+++ b/test/spec/integration/faker/googletag.js
@@ -91,4 +91,9 @@ export function disable() {
   window.googletag = undefined;
 }
 
+export function reset() {
+  disable();
+  enable();
+}
+
 enable();
diff --git a/test/spec/modules/priceFloors_spec.js b/test/spec/modules/priceFloors_spec.js
index 548d2789d3e..b3105dafc39 100644
--- a/test/spec/modules/priceFloors_spec.js
+++ b/test/spec/modules/priceFloors_spec.js
@@ -15,6 +15,7 @@ import {
   allowedFields
 } from 'modules/priceFloors.js';
 import events from 'src/events.js';
+import * as mockGpt from '../integration/faker/googletag.js';
 
 describe('the price floors module', function () {
   let logErrorSpy;
@@ -398,6 +399,84 @@ describe('the price floors module', function () {
         matchingFloor: 5.0
       });
     });
+    describe('with gpt enabled', function () {
+      let gptFloorData;
+      beforeEach(function () {
+        gptFloorData = {
+          currency: 'USD',
+          schema: {
+            fields: ['gptSlot']
+          },
+          values: {
+            '/12345/sports/soccer': 1.1,
+            '/12345/sports/basketball': 2.2,
+            '/12345/news/politics': 3.3,
+            '/12345/news/weather': 4.4,
+            '*': 5.5,
+          },
+          default: 0.5
+        };
+        // reset it so no lingering stuff from other test specs
+        mockGpt.reset();
+        mockGpt.makeSlot({
+          code: '/12345/sports/soccer',
+          divId: 'test_div_1'
+        });
+        mockGpt.makeSlot({
+          code: '/12345/sports/basketball',
+          divId: 'test_div_2'
+        });
+      });
+      afterEach(function () {
+        // reset it so no lingering stuff from other test specs
+        mockGpt.reset();
+      });
+      it('picks the right rule when looking for gptSlot', function () {
+        expect(getFirstMatchingFloor(gptFloorData, basicBidRequest)).to.deep.equal({
+          floorMin: 0,
+          floorRuleValue: 1.1,
+          matchingFloor: 1.1,
+          matchingData: '/12345/sports/soccer',
+          matchingRule: '/12345/sports/soccer'
+        });
+
+        let newBidRequest = { ...basicBidRequest, adUnitCode: 'test_div_2' }
+        expect(getFirstMatchingFloor(gptFloorData, newBidRequest)).to.deep.equal({
+          floorMin: 0,
+          floorRuleValue: 2.2,
+          matchingFloor: 2.2,
+          matchingData: '/12345/sports/basketball',
+          matchingRule: '/12345/sports/basketball'
+        });
+      });
+      it('picks the gptSlot from the bidRequest and does not call the slotMatching', function () {
+        const newBidRequest1 = { ...basicBidRequest };
+        utils.deepSetValue(newBidRequest1, 'ortb2Imp.ext.data.adserver', {
+          name: 'gam',
+          adslot: '/12345/news/politics'
+        })
+        expect(getFirstMatchingFloor(gptFloorData, newBidRequest1)).to.deep.equal({
+          floorMin: 0,
+          floorRuleValue: 3.3,
+          matchingFloor: 3.3,
+          matchingData: '/12345/news/politics',
+          matchingRule: '/12345/news/politics'
+        });
+
+        const newBidRequest2 = { ...basicBidRequest, adUnitCode: 'test_div_2' };
+        utils.deepSetValue(newBidRequest2, 'ortb2Imp.ext.data.adserver', {
+          name: 'gam',
+          adslot: '/12345/news/weather'
+        })
+        expect(getFirstMatchingFloor(gptFloorData, newBidRequest2)).to.deep.equal({
+          floorMin: 0,
+          floorRuleValue: 4.4,
+          matchingFloor: 4.4,
+          matchingData: '/12345/news/weather',
+          matchingRule: '/12345/news/weather'
+        });
+      });
+    });
   });
   describe('pre-auction tests', function () {
     let exposedAdUnits;