diff --git a/modules/prebidServerBidAdapter/index.js b/modules/prebidServerBidAdapter/index.js
index 673e92f709b..6b4d3a329e5 100644
--- a/modules/prebidServerBidAdapter/index.js
+++ b/modules/prebidServerBidAdapter/index.js
@@ -105,45 +105,45 @@ config.setDefaults({
 });
 
 /**
- * @param {S2SConfig} option
+ * @param {S2SConfig} s2sConfig
  * @return {boolean}
  */
-function updateConfigDefaultVendor(option) {
-  if (option.defaultVendor) {
-    let vendor = option.defaultVendor;
-    let optionKeys = Object.keys(option);
+function updateConfigDefaults(s2sConfig) {
+  if (s2sConfig.defaultVendor) {
+    let vendor = s2sConfig.defaultVendor;
+    let optionKeys = Object.keys(s2sConfig);
     if (S2S_VENDORS[vendor]) {
       // vendor keys will be set if either: the key was not specified by user
       // or if the user did not set their own distinct value (ie using the system default) to override the vendor
       Object.keys(S2S_VENDORS[vendor]).forEach((vendorKey) => {
-        if (s2sDefaultConfig[vendorKey] === option[vendorKey] || !includes(optionKeys, vendorKey)) {
-          option[vendorKey] = S2S_VENDORS[vendor][vendorKey];
+        if (s2sDefaultConfig[vendorKey] === s2sConfig[vendorKey] || !includes(optionKeys, vendorKey)) {
+          s2sConfig[vendorKey] = S2S_VENDORS[vendor][vendorKey];
         }
       });
     } else {
       logError('Incorrect or unavailable prebid server default vendor option: ' + vendor);
       return false;
     }
+  } else {
+    if (s2sConfig.adapter == null) {
+      s2sConfig.adapter = 'prebidServer';
+    }
   }
-  // this is how we can know if user / defaultVendor has set it, or if we should default to false
-  return option.enabled = typeof option.enabled === 'boolean' ? option.enabled : false;
+  return true;
 }
 
 /**
- * @param {S2SConfig} option
+ * @param {S2SConfig} s2sConfig
  * @return {boolean}
  */
-function validateConfigRequiredProps(option) {
-  const keys = Object.keys(option);
-  if (['accountId', 'endpoint'].filter(key => {
-    if (!includes(keys, key)) {
+function validateConfigRequiredProps(s2sConfig) {
+  for (const key of ['accountId', 'endpoint']) {
+    if (s2sConfig[key] == null) {
       logError(key + ' missing in server to server config');
-      return true;
+      return false;
     }
-    return false;
-  }).length > 0) {
-    return false;
   }
+  return true;
 }
 
 // temporary change to modify the s2sConfig for new format used for endpoint URLs;
@@ -164,40 +164,43 @@ function formatUrlParams(option) {
   });
 }
 
-/**
- * @param {(S2SConfig[]|S2SConfig)} options
- */
-function setS2sConfig(options) {
+export function validateConfig(options) {
   if (!options) {
     return;
   }
-  const normalizedOptions = Array.isArray(options) ? options : [options];
-
-  const activeBidders = [];
-  const optionsValid = normalizedOptions.every((option, i, array) => {
-    formatUrlParams(option);
-    const updateSuccess = updateConfigDefaultVendor(option);
-    if (updateSuccess !== false) {
-      const valid = validateConfigRequiredProps(option);
-      if (valid !== false) {
-        if (Array.isArray(option['bidders'])) {
-          array[i]['bidders'] = option['bidders'].filter(bidder => {
-            if (activeBidders.indexOf(bidder) === -1) {
-              activeBidders.push(bidder);
-              return true;
-            }
+  options = Array.isArray(options) ? options : [options];
+  const activeBidders = new Set();
+  return options.filter(s2sConfig => {
+    formatUrlParams(s2sConfig);
+    if (
+      updateConfigDefaults(s2sConfig) &&
+      validateConfigRequiredProps(s2sConfig) &&
+      s2sConfig.enabled
+    ) {
+      if (Array.isArray(s2sConfig.bidders)) {
+        s2sConfig.bidders = s2sConfig.bidders.filter(bidder => {
+          if (activeBidders.has(bidder)) {
             return false;
-          });
-        }
-        return true;
+          } else {
+            activeBidders.add(bidder);
+            return true;
+          }
+        })
       }
+      return true;
+    } else {
+      logWarn('prebidServer: s2s config is disabled', s2sConfig);
     }
-    logWarn('prebidServer: s2s config is disabled');
-    return false;
-  });
+  })
+}
 
-  if (optionsValid) {
-    return _s2sConfigs = normalizedOptions;
+/**
+ * @param {(S2SConfig[]|S2SConfig)} options
+ */
+function setS2sConfig(options) {
+  options = validateConfig(options);
+  if (options.length) {
+    _s2sConfigs = options;
   }
 }
 getConfig('s2sConfig', ({s2sConfig}) => setS2sConfig(s2sConfig));
diff --git a/test/spec/modules/prebidServerBidAdapter_spec.js b/test/spec/modules/prebidServerBidAdapter_spec.js
index fb1b62b9dc6..a67119e72d4 100644
--- a/test/spec/modules/prebidServerBidAdapter_spec.js
+++ b/test/spec/modules/prebidServerBidAdapter_spec.js
@@ -4,6 +4,7 @@ import {
   PrebidServer as Adapter,
   resetSyncedStatus,
   resetWurlMap,
+  validateConfig,
   s2sDefaultConfig
 } from 'modules/prebidServerBidAdapter/index.js';
 import adapterManager, {PBS_ADAPTER_NAME} from 'src/adapterManager.js';
@@ -564,6 +565,35 @@ function addFpdEnrichmentsToS2SRequest(s2sReq, bidderRequests) {
   }
 }
 
+describe('s2s configuration', () => {
+  let cfg1, cfg2;
+  beforeEach(() => {
+    cfg1 = {
+      enabled: true,
+      bidders: ['bidderB'],
+      accountId: '123456',
+      endpoint: {
+        p1Consent: 'first.endpoint'
+      }
+    };
+    cfg2 = {
+      enabled: true,
+      bidders: ['bidderA'],
+      accountId: '123456',
+      endpoint: {
+        p1Consent: 'second.endpoint',
+      }
+    };
+  })
+  it('sets prebid server adapter by default', () => {
+    expect(validateConfig(cfg1)[0].adapter).to.eql('prebidServer');
+  });
+  it('filters out disabled configs', () => {
+    cfg1.enabled = false;
+    expect(validateConfig([cfg1, cfg2])).to.eql([cfg2]);
+  })
+});
+
 describe('S2S Adapter', function () {
   let adapter,
     addBidResponse = sinon.spy(),