diff --git a/example/front_matter.dart b/example/front_matter.dart
index 1ba1455..835a5b2 100644
--- a/example/front_matter.dart
+++ b/example/front_matter.dart
@@ -2,7 +2,7 @@ import 'dart:io';
 import 'package:front_matter/front_matter.dart' as fm;
 
 // Example 1 - Parse a string.
-void example1() async {
+Future<void> example1() async {
   var file = File('example/hello-world.md');
   var fileContents = await file.readAsString();
 
@@ -14,7 +14,7 @@ void example1() async {
 }
 
 // Example 2 - Read a file and parse its contents.
-void example2() async {
+Future<void> example2() async {
   var doc = await fm.parseFile('example/hello-world.md');
 
   print("The author is ${doc.data['author']}");
diff --git a/lib/src/front_matter.dart b/lib/src/front_matter.dart
index 75678ff..9c008bb 100644
--- a/lib/src/front_matter.dart
+++ b/lib/src/front_matter.dart
@@ -27,11 +27,10 @@ Future<FrontMatterDocument> parseFile(String path,
     return parser(text, delimiter: delimiter);
   } catch (e) {
     // Handle downstream errors, or throw one if file is not readable as text.
-    switch (e.message) {
-      case invalidYamlError:
-        rethrow;
-      default:
-        throw FrontMatterException(fileTypeError);
-    }
+    if (e is FrontMatterException && e.message == invalidYamlError) {
+      rethrow;
+    } else {
+      throw FrontMatterException(fileTypeError);
+    } 
   }
 }
diff --git a/lib/src/front_matter_document.dart b/lib/src/front_matter_document.dart
index b509a94..976c8d6 100644
--- a/lib/src/front_matter_document.dart
+++ b/lib/src/front_matter_document.dart
@@ -6,10 +6,10 @@ class FrontMatterDocument {
   String value;
 
   /// The parsed [content] from the [value].
-  String content;
+  String? content;
 
   /// The parsed YAML front matter as a [YamlMap].
-  YamlMap data;
+  YamlMap data = YamlMap();
 
   FrontMatterDocument(this.value);
 
diff --git a/lib/src/parser.dart b/lib/src/parser.dart
index 694c6bf..5bd9eaf 100644
--- a/lib/src/parser.dart
+++ b/lib/src/parser.dart
@@ -8,7 +8,7 @@ import 'front_matter_exception.dart';
 /// `data` [YamlMap], and the remaining `content` [String].
 ///
 /// Throws a [FrontMatterException] if front matter contains invalid YAML.
-FrontMatterDocument parser(String text, {String delimiter}) {
+FrontMatterDocument parser(String text, {required String delimiter}) {
   var doc = FrontMatterDocument(text);
 
   // Remove any leading whitespace.
diff --git a/pubspec.yaml b/pubspec.yaml
index cc2e0a5..57fc3ec 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,12 +1,11 @@
 name: front_matter
 version: 1.1.0
 description: A front matter parser that extracts YAML metadata from the start of a file or string.
-author: izolate <izolate@gmail.com>
 homepage: https://github.com/izolate/front-matter
 documentation: https://github.com/izolate/front-matter/blob/master/README.md
 environment:
-  sdk: '>=2.0.0 <3.0.0'
+  sdk: '>=3.0.0 <4.0.0'
 dependencies:
-  yaml: ^2.1.15
+  yaml: ^3.1.2
 dev_dependencies:
-  test: ^1.6.2
+  test: ^1.21.6
diff --git a/test/front_matter_test.dart b/test/front_matter_test.dart
index e2bd7f2..8cccd25 100644
--- a/test/front_matter_test.dart
+++ b/test/front_matter_test.dart
@@ -1,6 +1,5 @@
 import 'package:test/test.dart';
 import 'package:front_matter/front_matter.dart' as fm;
-import 'package:front_matter/src/front_matter.dart';
 import 'package:front_matter/src/front_matter_document.dart';
 import 'package:front_matter/src/front_matter_exception.dart';