diff --git a/packages/url_launcher/url_launcher/CHANGELOG.md b/packages/url_launcher/url_launcher/CHANGELOG.md
index 5c826e6552e8..3d8dd24f8b5b 100644
--- a/packages/url_launcher/url_launcher/CHANGELOG.md
+++ b/packages/url_launcher/url_launcher/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 5.4.8
+
+* Initialize `previousAutomaticSystemUiAdjustment` in launch method.
+
 ## 5.4.7
 
 * Update lower bound of dart dependency to 2.1.0.
diff --git a/packages/url_launcher/url_launcher/lib/url_launcher.dart b/packages/url_launcher/url_launcher/lib/url_launcher.dart
index 97af77143936..2ce725da8642 100644
--- a/packages/url_launcher/url_launcher/lib/url_launcher.dart
+++ b/packages/url_launcher/url_launcher/lib/url_launcher.dart
@@ -73,7 +73,9 @@ Future<bool> launch(
         message: 'To use webview or safariVC, you need to pass'
             'in a web URL. This $urlString is not a web URL.');
   }
-  bool previousAutomaticSystemUiAdjustment;
+
+  /// [true] so that ui is automatically computed if [statusBarBrightness] is set.
+  bool previousAutomaticSystemUiAdjustment = true;
   if (statusBarBrightness != null &&
       defaultTargetPlatform == TargetPlatform.iOS) {
     previousAutomaticSystemUiAdjustment =
@@ -92,6 +94,7 @@ Future<bool> launch(
     universalLinksOnly: universalLinksOnly ?? false,
     headers: headers ?? <String, String>{},
   );
+  assert(previousAutomaticSystemUiAdjustment != null);
   if (statusBarBrightness != null) {
     WidgetsBinding.instance.renderView.automaticSystemUiAdjustment =
         previousAutomaticSystemUiAdjustment;
diff --git a/packages/url_launcher/url_launcher/pubspec.yaml b/packages/url_launcher/url_launcher/pubspec.yaml
index d038c41e0da4..c09dcbfea381 100644
--- a/packages/url_launcher/url_launcher/pubspec.yaml
+++ b/packages/url_launcher/url_launcher/pubspec.yaml
@@ -2,7 +2,7 @@ name: url_launcher
 description: Flutter plugin for launching a URL on Android and iOS. Supports
   web, phone, SMS, and email schemes.
 homepage: https://github.com/flutter/plugins/tree/master/packages/url_launcher/url_launcher
-version: 5.4.7
+version: 5.4.8
 
 flutter:
   plugin:
diff --git a/packages/url_launcher/url_launcher/test/url_launcher_test.dart b/packages/url_launcher/url_launcher/test/url_launcher_test.dart
index 19022f1edfb6..9d01b43d8e72 100644
--- a/packages/url_launcher/url_launcher/test/url_launcher_test.dart
+++ b/packages/url_launcher/url_launcher/test/url_launcher_test.dart
@@ -205,6 +205,21 @@ void main() {
       await launchResult;
       expect(binding.renderView.automaticSystemUiAdjustment, isTrue);
     });
+
+    test('sets automaticSystemUiAdjustment to not be null', () async {
+      final TestWidgetsFlutterBinding binding =
+          TestWidgetsFlutterBinding.ensureInitialized();
+      debugDefaultTargetPlatformOverride = TargetPlatform.android;
+      expect(binding.renderView.automaticSystemUiAdjustment, true);
+      final Future<bool> launchResult =
+          launch('http://flutter.dev/', statusBarBrightness: Brightness.dark);
+
+      // The automaticSystemUiAdjustment should be set before the launch
+      // and equal to true after the launch result is complete.
+      expect(binding.renderView.automaticSystemUiAdjustment, true);
+      await launchResult;
+      expect(binding.renderView.automaticSystemUiAdjustment, true);
+    });
   });
 }