diff --git a/src/actions/receive-profile.ts b/src/actions/receive-profile.ts
index 15a7903dea..cd392613fa 100644
--- a/src/actions/receive-profile.ts
+++ b/src/actions/receive-profile.ts
@@ -1416,9 +1416,9 @@ export function retrieveProfilesToCompare(
     dispatch(waitingForProfileFromUrl());
 
     try {
-      // First we get a state from each URL. From these states we'll get all the
-      // data we need to fetch and process the profiles.
-      const profileStates = await Promise.all(
+      // Fetch each profile first so we can pass the upgrade info to
+      // stateFromLocation, allowing URL upgraders to work correctly.
+      const profilesAndStates = await Promise.all(
         profileViewUrls.map(async (url) => {
           if (
             url.startsWith('https://perfht.ml/') ||
@@ -1427,28 +1427,23 @@ export function retrieveProfilesToCompare(
           ) {
             url = await expandUrl(url);
           }
-          // TODO: Pass the profileUpgradeInfo here. See #5871.
-          return stateFromLocation(new URL(url));
-        })
-      );
 
-      // Then we retrieve the profiles from the online store, and unserialize
-      // and process them if needed.
-      const promises = profileStates.map(
-        async ({ dataSource, hash, profileUrl }) => {
+          const preliminaryState = stateFromLocation(new URL(url));
+          let { profileUrl } = preliminaryState;
+          const { dataSource, hash } = preliminaryState;
+
           switch (dataSource) {
             case 'public':
-              // Use a URL from the public store.
               profileUrl = getProfileUrlForHash(hash);
               break;
             case 'from-url':
-              // Use the profile URL in the decoded state, decoded from the input URL.
               break;
             default:
               throw new Error(
                 'Only public uploaded profiles are supported by the comparison function.'
               );
           }
+
           const response: ProfileOrZip = await _fetchProfile({
             url: profileUrl,
             onTemporaryError: (e: TemporaryError) => {
@@ -1458,18 +1453,27 @@ export function retrieveProfilesToCompare(
           if (response.responseType !== 'PROFILE') {
             throw new Error('Expected to receive a profile from _fetchProfile');
           }
-          const serializedProfile = response.profile;
 
-          const profile =
-            unserializeProfileOfArbitraryFormat(serializedProfile);
-          return profile;
-        }
+          const upgradeInfo: ProfileUpgradeInfo = {};
+          const profile = await unserializeProfileOfArbitraryFormat(
+            response.profile,
+            profileUrl,
+            upgradeInfo
+          );
+
+          const profileState = stateFromLocation(new URL(url), {
+            profile,
+            upgradeInfo,
+          });
+
+          return { profile, profileState };
+        })
       );
 
-      // Once all profiles have been fetched and unserialized, we can start
-      // pushing them to a brand new profile. This resulting profile will keep
-      // only the 2 selected threads from the 2 profiles.
-      const profiles = await Promise.all(promises);
+      const profiles = profilesAndStates.map(({ profile }) => profile);
+      const profileStates = profilesAndStates.map(
+        ({ profileState }) => profileState
+      );
 
       const {
         profile: resultProfile,