--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -233,17 +233,17 @@ pref("general.autoScroll", true);
 pref("browser.shell.checkDefaultBrowser", true);
 pref("browser.shell.shortcutFavicons",true);
 pref("browser.shell.mostRecentDateSetAsDefault", "");
 #ifdef RELEASE_OR_BETA
 pref("browser.shell.skipDefaultBrowserCheckOnFirstRun", false);
 #else
 pref("browser.shell.skipDefaultBrowserCheckOnFirstRun", true);
 #endif
-pref("browser.shell.skipDefaultBrowserCheck", true);
+pref("browser.shell.didSkipDefaultBrowserCheckOnFirstRun", false);
 pref("browser.shell.defaultBrowserCheckCount", 0);
 pref("browser.defaultbrowser.notificationbar", false);
 
 // 0 = blank, 1 = home (browser.startup.homepage), 2 = last visited page, 3 = resume previous browser session
 // The behavior of option 3 is detailed at: http://wiki.mozilla.org/Session_Restore
 pref("browser.startup.page",                1);
 pref("browser.startup.homepage",            "chrome://branding/locale/browserconfig.properties");
 // Whether we should skip the homepage when opening the first-run page

--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -1065,17 +1065,17 @@ BrowserGlue.prototype = {
 
     // Perform default browser checking.
     if (ShellService) {
       let shouldCheck = AppConstants.DEBUG ? false :
                                              ShellService.shouldCheckDefaultBrowser;
 
       const skipDefaultBrowserCheck =
         Services.prefs.getBoolPref("browser.shell.skipDefaultBrowserCheckOnFirstRun") &&
-        Services.prefs.getBoolPref("browser.shell.skipDefaultBrowserCheck");
+        !Services.prefs.getBoolPref("browser.shell.didSkipDefaultBrowserCheckOnFirstRun");
 
       const usePromptLimit = !AppConstants.RELEASE_OR_BETA;
       let promptCount =
         usePromptLimit ? Services.prefs.getIntPref("browser.shell.defaultBrowserCheckCount") : 0;
 
       let willRecoverSession = false;
       try {
         let ss = Cc["@mozilla.org/browser/sessionstartup;1"].
@@ -1099,17 +1099,17 @@ BrowserGlue.prototype = {
       }
 
       let willPrompt = shouldCheck && !isDefault && !willRecoverSession;
 
       // Skip the "Set Default Browser" check during first-run or after the
       // browser has been run a few times.
       if (willPrompt) {
         if (skipDefaultBrowserCheck) {
-          Services.prefs.setBoolPref("browser.shell.skipDefaultBrowserCheck", false);
+          Services.prefs.setBoolPref("browser.shell.didSkipDefaultBrowserCheckOnFirstRun", true);
           willPrompt = false;
         } else {
           promptCount++;
         }
         if (usePromptLimit && promptCount > 3) {
           willPrompt = false;
         }
       }
@@ -1661,18 +1661,19 @@ BrowserGlue.prototype = {
     let clickCallback = (subject, topic, data) => {
       if (topic != "alertclickcallback")
         return;
       this._openPreferences("sync");
     }
     AlertsService.showAlertNotification(null, title, body, true, null, clickCallback);
   },
 
+  // eslint-disable-next-line complexity
   _migrateUI: function BG__migrateUI() {
-    const UI_VERSION = 44;
+    const UI_VERSION = 45;
     const BROWSER_DOCURL = "chrome://browser/content/browser.xul";
 
     let currentUIVersion;
     if (Services.prefs.prefHasUserValue("browser.migration.version")) {
       currentUIVersion = Services.prefs.getIntPref("browser.migration.version");
     } else {
       // This is a new profile, nothing to migrate.
       Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
@@ -1956,16 +1957,25 @@ BrowserGlue.prototype = {
 
       Services.prefs.setBoolPref("toolkit.cosmeticAnimations.enabled", animate);
 
       Services.prefs.clearUserPref("browser.tabs.animate");
       Services.prefs.clearUserPref("browser.fullscreen.animate");
       Services.prefs.clearUserPref("alerts.disableSlidingEffect");
     }
 
+    if (currentUIVersion < 45) {
+      const LEGACY_PREF = "browser.shell.skipDefaultBrowserCheck";
+      if (Services.prefs.prefHasUserValue(LEGACY_PREF)) {
+        Services.prefs.setBoolPref("browser.shell.didSkipDefaultBrowserCheckOnFirstRun",
+                                   !Services.prefs.getBoolPref(LEGACY_PREF));
+        Services.prefs.clearUserPref(LEGACY_PREF);
+      }
+    }
+
     // Update the migration version.
     Services.prefs.setIntPref("browser.migration.version", UI_VERSION);
   },
 
   // ------------------------------
   // public nsIBrowserGlue members
   // ------------------------------