diff --git a/packages/pigeon/CHANGELOG.md b/packages/pigeon/CHANGELOG.md
index a87e4e99eee6..8e387e1da412 100644
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 27.1.1
+
+* Fixes validation bug where empty classes without `sealed` keyword were not correctly flagged with an error.
+
 ## 27.1.0
 
 * [swift] Adds `CaseIterable` conformance to generated enums.
diff --git a/packages/pigeon/lib/src/generator_tools.dart b/packages/pigeon/lib/src/generator_tools.dart
index 4cc20cfd1cfa..dbc56d4823b8 100644
--- a/packages/pigeon/lib/src/generator_tools.dart
+++ b/packages/pigeon/lib/src/generator_tools.dart
@@ -15,7 +15,7 @@ import 'generator.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '27.1.0';
+const String pigeonVersion = '27.1.1';
 
 /// Default plugin package name.
 const String defaultPluginPackageName = 'dev.flutter.pigeon';
diff --git a/packages/pigeon/lib/src/pigeon_lib_internal.dart b/packages/pigeon/lib/src/pigeon_lib_internal.dart
index b9607e12f528..b4141fbb6c9e 100644
--- a/packages/pigeon/lib/src/pigeon_lib_internal.dart
+++ b/packages/pigeon/lib/src/pigeon_lib_internal.dart
@@ -619,6 +619,25 @@ List<Error> _validateAst(Root root, String source) {
         ),
       );
     }
+    if (classDefinition.isSealed) {
+      if (classDefinition.fields.isNotEmpty) {
+        result.add(
+          Error(message: 'Sealed class: "${classDefinition.name}" must not contain fields.'),
+        );
+      }
+    }
+    if (classDefinition.fields.isEmpty && !classDefinition.isSealed) {
+      result.add(
+        Error(message: 'Class: "${classDefinition.name}" must contain fields or be sealed.'),
+      );
+    }
+    if (classDefinition.superClass != null) {
+      if (!classDefinition.superClass!.isSealed) {
+        result.add(
+          Error(message: 'Child class: "${classDefinition.name}" must extend a sealed class.'),
+        );
+      }
+    }
     for (final NamedType field in getFieldsInSerializationOrder(classDefinition)) {
       final String? matchingPrefix = _findMatchingPrefixOrNull(
         field.name,
@@ -644,26 +663,6 @@ List<Error> _validateAst(Root root, String source) {
           ),
         );
       }
-      if (classDefinition.isSealed) {
-        if (classDefinition.fields.isNotEmpty) {
-          result.add(
-            Error(
-              message: 'Sealed class: "${classDefinition.name}" must not contain fields.',
-              lineNumber: _calculateLineNumberNullable(source, field.offset),
-            ),
-          );
-        }
-      }
-      if (classDefinition.superClass != null) {
-        if (!classDefinition.superClass!.isSealed) {
-          result.add(
-            Error(
-              message: 'Child class: "${classDefinition.name}" must extend a sealed class.',
-              lineNumber: _calculateLineNumberNullable(source, field.offset),
-            ),
-          );
-        }
-      }
     }
   }
 
@@ -1805,22 +1804,21 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
               lineNumber: calculateLineNumber(source, node.offset),
             ),
           );
-        } else {
-          final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
-          final String name = node.fields.variables[0].name.lexeme;
-          final field = NamedType(
-            type: TypeDeclaration(
-              baseName: _getNamedTypeQualifiedName(type),
-              isNullable: type.question != null,
-              typeArguments: _typeAnnotationsToTypeArguments(typeArguments),
-            ),
-            name: name,
-            offset: node.offset,
-            defaultValue: _currentClassDefaultValues[name],
-            documentationComments: _documentationCommentsParser(node.documentationComment?.tokens),
-          );
-          _currentClass!.fields.add(field);
         }
+        final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
+        final String name = node.fields.variables[0].name.lexeme;
+        final field = NamedType(
+          type: TypeDeclaration(
+            baseName: _getNamedTypeQualifiedName(type),
+            isNullable: type.question != null,
+            typeArguments: _typeAnnotationsToTypeArguments(typeArguments),
+          ),
+          name: name,
+          offset: node.offset,
+          defaultValue: _currentClassDefaultValues[name],
+          documentationComments: _documentationCommentsParser(node.documentationComment?.tokens),
+        );
+        _currentClass!.fields.add(field);
       } else {
         _errors.add(
           Error(
@@ -1969,23 +1967,22 @@ class RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             lineNumber: calculateLineNumber(source, node.offset),
           ),
         );
-      } else {
-        final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
-        (_currentApi as AstProxyApi?)!.fields.add(
-          ApiField(
-            type: TypeDeclaration(
-              baseName: _getNamedTypeQualifiedName(type),
-              isNullable: type.question != null,
-              typeArguments: _typeAnnotationsToTypeArguments(typeArguments),
-            ),
-            name: node.fields.variables[0].name.lexeme,
-            isAttached: _hasMetadata(node.metadata, 'attached') || isStatic,
-            isStatic: isStatic,
-            offset: node.offset,
-            documentationComments: _documentationCommentsParser(node.documentationComment?.tokens),
-          ),
-        );
       }
+      final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
+      (_currentApi as AstProxyApi?)!.fields.add(
+        ApiField(
+          type: TypeDeclaration(
+            baseName: _getNamedTypeQualifiedName(type),
+            isNullable: type.question != null,
+            typeArguments: _typeAnnotationsToTypeArguments(typeArguments),
+          ),
+          name: node.fields.variables[0].name.lexeme,
+          isAttached: _hasMetadata(node.metadata, 'attached') || isStatic,
+          isStatic: isStatic,
+          offset: node.offset,
+          documentationComments: _documentationCommentsParser(node.documentationComment?.tokens),
+        ),
+      );
     }
   }
 }
diff --git a/packages/pigeon/pubspec.yaml b/packages/pigeon/pubspec.yaml
index 65afaca2890f..bf3b9563ca90 100644
--- a/packages/pigeon/pubspec.yaml
+++ b/packages/pigeon/pubspec.yaml
@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 27.1.0 # This must match the version in lib/src/generator_tools.dart
+version: 27.1.1 # This must match the version in lib/src/generator_tools.dart
 
 environment:
   sdk: ^3.10.0
diff --git a/packages/pigeon/test/pigeon_lib_test.dart b/packages/pigeon/test/pigeon_lib_test.dart
index 7c319672e81d..df0f12d29486 100644
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@@ -215,6 +215,23 @@ abstract class Api {
     expect(results.errors[0].message, contains('dynamic'));
   });
 
+  test('empty class error', () {
+    const source = '''
+class EmptyClass {}
+
+@HostApi()
+abstract class Api {
+  void foo(EmptyClass empty);
+}
+''';
+    final ParseResults results = parseSource(source);
+    expect(results.errors, hasLength(1));
+    expect(
+      results.errors[0].message,
+      contains('Class: "EmptyClass" must contain fields or be sealed.'),
+    );
+  });
+
   test('Only allow one api annotation', () {
     const source = '''
 @HostApi()
@@ -1703,7 +1720,9 @@ abstract class EventChannelApi {
   group('sealed inheritance validation', () {
     test('super class must be sealed', () {
       const code = '''
-class DataClass {}
+class DataClass {
+  int? someField;
+}
 class ChildClass extends DataClass {
   ChildClass(this.input);
   int input;