--- a/browser/components/BrowserGlue.jsm
+++ b/browser/components/BrowserGlue.jsm
@@ -3239,17 +3239,17 @@ BrowserGlue.prototype = {
       );
     });
   },
 
   // eslint-disable-next-line complexity
   _migrateUI: function BG__migrateUI() {
     // Use an increasing number to keep track of the current migration state.
     // Completely unrelated to the current Firefox release number.
-    const UI_VERSION = 97;
+    const UI_VERSION = 98;
     const BROWSER_DOCURL = AppConstants.BROWSER_CHROME_URL;
 
     if (!Services.prefs.prefHasUserValue("browser.migration.version")) {
       // This is a new profile, nothing to migrate.
       Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
       this._isNewProfile = true;
       return;
     }
@@ -3867,16 +3867,20 @@ BrowserGlue.prototype = {
         );
       } else {
         // The last remaining case is if they customized both values, in which
         // case also we leave the "migration complete" percentage at 100, as no
         // further migration is needed.
       }
     }
 
+    if (currentUIVersion < 98) {
+      Services.prefs.clearUserPref("browser.search.cohort");
+    }
+
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },
 
   _maybeShowDefaultBrowserPrompt() {
     DefaultBrowserCheck.willCheckDefaultBrowser(/* isStartupCheck */ true).then(
       async willPrompt => {
         let { DefaultBrowserNotification } = ChromeUtils.import(

new file mode 100644
--- /dev/null
+++ b/browser/components/tests/unit/test_browserGlue_migration_no_errors.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Since various migrations in BrowserGlue are sometimes trivial, e.g. just
+ * clearing a pref, it does not feel necessary to write tests for each of those.
+ *
+ * However, ensuring we have at least some coverage to check for errors, e.g.
+ * typos, is a good idea, hence this test.
+ *
+ * If your migration is more complex that clearing a couple of prefs, you
+ * should consider adding your own BrowserGlue migration test.
+ */
+const TOPIC_BROWSERGLUE_TEST = "browser-glue-test";
+const TOPICDATA_BROWSERGLUE_TEST = "force-ui-migration";
+
+const gBrowserGlue = Cc["@mozilla.org/browser/browserglue;1"].getService(
+  Ci.nsIObserver
+);
+
+// Set the migration value to 1, to ensure that the migration code is called,
+// and so that this doesn't need updating every time we obsolete old tests.
+Services.prefs.setIntPref("browser.migration.version", 1);
+
+add_task(async function test_no_errors() {
+  // Simulate a migration.
+  gBrowserGlue.observe(
+    null,
+    TOPIC_BROWSERGLUE_TEST,
+    TOPICDATA_BROWSERGLUE_TEST
+  );
+
+  Assert.ok(true, "should have run the migration with no errors");
+});

--- a/browser/components/tests/unit/xpcshell.ini
+++ b/browser/components/tests/unit/xpcshell.ini
@@ -2,9 +2,10 @@
 head = head.js
 firefox-appdir = browser
 skip-if = toolkit == 'android'
 support-files =
   distribution.ini
 
 [test_distribution.js]
 [test_distribution_cachedexistence.js]
+[test_browserGlue_migration_no_errors.js]
 [test_browserGlue_migration_social_cleanup.js]