diff --git a/protobuf/lib/src/protobuf/builder_info.dart b/protobuf/lib/src/protobuf/builder_info.dart
index 95fa3b003..91913fbac 100644
--- a/protobuf/lib/src/protobuf/builder_info.dart
+++ b/protobuf/lib/src/protobuf/builder_info.dart
@@ -44,7 +44,7 @@ class BuilderInfo {
     var index = byIndex.length;
     final fieldInfo = (tagNumber == 0)
         ? FieldInfo.dummy(index)
-        : FieldInfo<T>(name, tagNumber, index, fieldType,
+        : FieldInfo<T, T>(name, tagNumber, index, fieldType,
             defaultOrMaker: defaultOrMaker,
             subBuilder: subBuilder,
             valueOf: valueOf,
@@ -77,7 +77,7 @@ class BuilderInfo {
       List<ProtobufEnum> enumValues,
       {String protoName}) {
     var index = byIndex.length;
-    _addField(FieldInfo<T>.repeated(
+    _addField(FieldInfo<T, List<T>>.repeated(
         name, tagNumber, index, fieldType, check, subBuilder,
         valueOf: valueOf, enumValues: enumValues, protoName: protoName));
   }
diff --git a/protobuf/lib/src/protobuf/extension.dart b/protobuf/lib/src/protobuf/extension.dart
index cecc2574b..cea8be5f2 100644
--- a/protobuf/lib/src/protobuf/extension.dart
+++ b/protobuf/lib/src/protobuf/extension.dart
@@ -5,7 +5,7 @@
 part of protobuf;
 
 /// An object representing an extension field.
-class Extension<T> extends FieldInfo<T> {
+class Extension<T, U> extends FieldInfo<T, U> {
   final String extendee;
 
   Extension(this.extendee, String name, int tagNumber, int fieldType,
diff --git a/protobuf/lib/src/protobuf/extension_field_set.dart b/protobuf/lib/src/protobuf/extension_field_set.dart
index e516a9d8d..9e3a755a2 100644
--- a/protobuf/lib/src/protobuf/extension_field_set.dart
+++ b/protobuf/lib/src/protobuf/extension_field_set.dart
@@ -36,7 +36,7 @@ class _ExtensionFieldSet {
   ///
   /// If it doesn't exist, creates the list and saves the extension.
   /// Suitable for public API and decoders.
-  List<T> _ensureRepeatedField<T>(Extension<T> fi) {
+  List<T> _ensureRepeatedField<T, S>(Extension<T, S> fi) {
     assert(!_isReadOnly);
     assert(fi.isRepeated);
     assert(fi.extendee == _parent._messageName);
@@ -47,7 +47,7 @@ class _ExtensionFieldSet {
     return _addInfoAndCreateList(fi);
   }
 
-  List<T> _getList<T>(Extension<T> fi) {
+  List<T> _getList<T, S>(Extension<T, S> fi) {
     var value = _values[fi.tagNumber];
     if (value != null) return value as List<T>;
     if (_isReadOnly) return List<T>.unmodifiable(const []);
diff --git a/protobuf/lib/src/protobuf/field_info.dart b/protobuf/lib/src/protobuf/field_info.dart
index 1a52faf34..af2263232 100644
--- a/protobuf/lib/src/protobuf/field_info.dart
+++ b/protobuf/lib/src/protobuf/field_info.dart
@@ -5,7 +5,8 @@
 part of protobuf;
 
 /// An object representing a protobuf message field.
-class FieldInfo<T> {
+/// For a repeated field S is List<T> for a non-repeated field S=T.
+class FieldInfo<T, U> {
   FrozenPbList<T> _emptyList;
 
   /// Name of this field as the `json_name` reported by protoc.
@@ -24,9 +25,9 @@ class FieldInfo<T> {
 
   // Constructs the default value of a field.
   // (Only used for repeated fields where check is null.)
-  final MakeDefaultFunc makeDefault;
+  final U Function() makeDefault;
 
-  // Creates an empty message or group when decoding a message.
+  // Creates an empty message when decoding a message.
   // Not used for other types.
   // see GeneratedMessage._getEmptyMessage
   final CreateBuilderFunc subBuilder;
@@ -74,7 +75,7 @@ class FieldInfo<T> {
   FieldInfo.repeated(this.name, this.tagNumber, this.index, this.type,
       this.check, this.subBuilder,
       {this.valueOf, this.enumValues, String protoName})
-      : makeDefault = (() => PbList<T>(check: check)),
+      : makeDefault = (() => PbList<T>(check: check) as U),
         protoName = protoName ?? _unCamelCase(name) {
     assert(name != null);
     assert(tagNumber != null);
@@ -83,7 +84,7 @@ class FieldInfo<T> {
     assert(!_isEnum(type) || valueOf != null);
   }
 
-  static MakeDefaultFunc findMakeDefault(int type, dynamic defaultOrMaker) {
+  static S Function() findMakeDefault<S>(int type, dynamic defaultOrMaker) {
     if (defaultOrMaker == null) return PbFieldType._defaultForType(type);
     if (defaultOrMaker is MakeDefaultFunc) return defaultOrMaker;
     return () => defaultOrMaker;
@@ -101,9 +102,9 @@ class FieldInfo<T> {
 
   /// Returns a read-only default value for a field.
   /// (Unlike getField, doesn't create a repeated field.)
-  dynamic get readonlyDefault {
+  U get readonlyDefault {
     if (isRepeated) {
-      return _emptyList ??= FrozenPbList._([]);
+      return (_emptyList ??= FrozenPbList<T>._([])) as U;
     }
     return makeDefault();
   }
@@ -165,19 +166,19 @@ class FieldInfo<T> {
   /// be overridden by a mixin.
   List<T> _createRepeatedField(GeneratedMessage m) {
     assert(isRepeated);
-    return m.createRepeatedField<T>(tagNumber, this);
+    return m.createRepeatedField<T, U>(tagNumber, this);
   }
 
   /// Same as above, but allow a tighter typed List to be created.
   List<S> _createRepeatedFieldWithType<S extends T>(GeneratedMessage m) {
     assert(isRepeated);
-    return m.createRepeatedField<S>(tagNumber, this);
+    return m.createRepeatedField<S, U>(tagNumber, this);
   }
 
   /// Convenience method to thread this FieldInfo's reified type parameter to
   /// _FieldSet._ensureRepeatedField.
   List<T> _ensureRepeatedField(_FieldSet fs) {
-    return fs._ensureRepeatedField<T>(this);
+    return fs._ensureRepeatedField<T, U>(this);
   }
 
   @override
@@ -191,7 +192,7 @@ String _unCamelCase(String name) {
       _upperCase, (match) => '_${match.group(0).toLowerCase()}');
 }
 
-class MapFieldInfo<K, V> extends FieldInfo<PbMap<K, V>> {
+class MapFieldInfo<K, V> extends FieldInfo<PbMap<K, V>, PbMap<K, V>> {
   final int keyFieldType;
   final int valueFieldType;
 
diff --git a/protobuf/lib/src/protobuf/field_set.dart b/protobuf/lib/src/protobuf/field_set.dart
index 11df0c3db..5ff1635d2 100644
--- a/protobuf/lib/src/protobuf/field_set.dart
+++ b/protobuf/lib/src/protobuf/field_set.dart
@@ -236,7 +236,7 @@ class _FieldSet {
     return value;
   }
 
-  List<T> _getDefaultList<T>(FieldInfo<T> fi) {
+  List<T> _getDefaultList<T, U>(FieldInfo<T, U> fi) {
     assert(fi.isRepeated);
     if (_isReadOnly) return List.unmodifiable(const []);
 
@@ -359,11 +359,11 @@ class _FieldSet {
   /// Creates and stores the repeated field if it doesn't exist.
   /// If it's an extension and the list doesn't exist, validates and stores it.
   /// Suitable for decoders.
-  List<T> _ensureRepeatedField<T>(FieldInfo<T> fi) {
+  List<T> _ensureRepeatedField<T, U>(FieldInfo<T, U> fi) {
     assert(!_isReadOnly);
     assert(fi.isRepeated);
     if (fi.index == null) {
-      return _ensureExtensions()._ensureRepeatedField(fi);
+      return _ensureExtensions()._ensureRepeatedField(fi as Extension<T, U>);
     }
     var value = _getFieldOrNull(fi);
     if (value != null) return value as List<T>;
@@ -439,7 +439,7 @@ class _FieldSet {
   List<T> _$getList<T>(int index) {
     var value = _values[index];
     if (value != null) return value as List<T>;
-    return _getDefaultList<T>(_nonExtensionInfoByIndex(index));
+    return _getDefaultList<T, dynamic>(_nonExtensionInfoByIndex(index));
   }
 
   /// The implementation of a generated getter for map fields.
diff --git a/protobuf/lib/src/protobuf/generated_message.dart b/protobuf/lib/src/protobuf/generated_message.dart
index 13f4dfb6b..e1309fff3 100644
--- a/protobuf/lib/src/protobuf/generated_message.dart
+++ b/protobuf/lib/src/protobuf/generated_message.dart
@@ -313,7 +313,7 @@ abstract class GeneratedMessage {
   /// Returns the value of [extension].
   ///
   /// If not set, returns the extension's default value.
-  dynamic getExtension(Extension extension) {
+  U getExtension<T, U>(Extension<T, U> extension) {
     return _fieldSet._ensureExtensions()._getFieldOrDefault(extension);
   }
 
@@ -327,7 +327,7 @@ abstract class GeneratedMessage {
   /// that the protobuf can be encoded correctly, the returned List must
   /// validate all items added to it. This can most easily be done
   /// using the FieldInfo.check function.
-  List<T> createRepeatedField<T>(int tagNumber, FieldInfo<T> fi) {
+  List<T> createRepeatedField<T, U>(int tagNumber, FieldInfo<T, U> fi) {
     return PbList<T>(check: fi.check);
   }
 
diff --git a/protobuf/lib/src/protobuf/readonly_message.dart b/protobuf/lib/src/protobuf/readonly_message.dart
index 794f762ee..95cdb9107 100644
--- a/protobuf/lib/src/protobuf/readonly_message.dart
+++ b/protobuf/lib/src/protobuf/readonly_message.dart
@@ -17,7 +17,7 @@ abstract class ReadonlyMessageMixin {
 
   void clearField(int tagNumber) => _readonly('clearField');
 
-  List<T> createRepeatedField<T>(int tagNumber, FieldInfo<T> fi) {
+  List<T> createRepeatedField<T, U>(int tagNumber, FieldInfo<T, U> fi) {
     _readonly('createRepeatedField');
     return null; // not reached
   }
diff --git a/protoc_plugin/lib/extension_generator.dart b/protoc_plugin/lib/extension_generator.dart
index 2e30f3e41..9641ee927 100644
--- a/protoc_plugin/lib/extension_generator.dart
+++ b/protoc_plugin/lib/extension_generator.dart
@@ -97,6 +97,9 @@ class ExtensionGenerator {
     String name = _extensionName;
     var type = _field.baseType;
     var dartType = type.getDartType(fileGen);
+    var possiblyRepeatedDartType =
+        _field.isRepeated ? '$_coreImportPrefix.List<$dartType>' : dartType;
+    var typeArgs = '$dartType, $possiblyRepeatedDartType';
     String invocation;
     List<String> positionals = <String>[];
     positionals.add("'$_extendedFullName'");
@@ -107,7 +110,7 @@ class ExtensionGenerator {
     Map<String, String> named = <String, String>{};
     named['protoName'] = _field.quotedProtoName;
     if (_field.isRepeated) {
-      invocation = '$_protobufImportPrefix.Extension<$dartType>.repeated';
+      invocation = '$_protobufImportPrefix.Extension<$typeArgs>.repeated';
       named['check'] =
           '$_protobufImportPrefix.getCheckFunction(${_field.typeConstant})';
       if (type.isMessage || type.isGroup) {
@@ -117,7 +120,7 @@ class ExtensionGenerator {
         named['enumValues'] = '$dartType.values';
       }
     } else {
-      invocation = '$_protobufImportPrefix.Extension<$dartType>';
+      invocation = '$_protobufImportPrefix.Extension<$typeArgs>';
       named['defaultOrMaker'] = _field.generateDefaultFunction(fileGen);
       if (type.isMessage || type.isGroup) {
         named['subBuilder'] = '$dartType.create';
@@ -129,13 +132,14 @@ class ExtensionGenerator {
     }
     assert(invocation != null);
     out.printAnnotated(
-        'static final $_protobufImportPrefix.Extension $name = '
+        'static final $_protobufImportPrefix.Extension<$typeArgs> $name = '
         '$invocation(${ProtobufField._formatArguments(positionals, named)});\n',
         [
           NamedLocation(
               name: name,
               fieldPathSegment: List.from(fieldPath),
-              start: 'static final $_protobufImportPrefix.Extension '.length)
+              start: 'static final $_protobufImportPrefix.Extension<$typeArgs> '
+                  .length)
         ]);
   }
 }
diff --git a/protoc_plugin/lib/src/dart_options.pb.dart b/protoc_plugin/lib/src/dart_options.pb.dart
index ad2b620df..548f612bc 100644
--- a/protoc_plugin/lib/src/dart_options.pb.dart
+++ b/protoc_plugin/lib/src/dart_options.pb.dart
@@ -3,7 +3,7 @@
 //  source: dart_options.proto
 //
 // @dart = 2.3
-// ignore_for_file: camel_case_types,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
+// ignore_for_file: camel_case_types,unnecessary_const,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
 
 import 'dart:core' as $core;
 
@@ -110,38 +110,34 @@ class Imports extends $pb.GeneratedMessage {
 }
 
 class Dart_options {
-  static final $pb.Extension imports = $pb.Extension<Imports>(
-      'google.protobuf.FileOptions', 'imports', 28125061, $pb.PbFieldType.OM,
-      defaultOrMaker: Imports.getDefault, subBuilder: Imports.create);
-  static final $pb.Extension defaultMixin = $pb.Extension<$core.String>(
-      'google.protobuf.FileOptions',
-      'defaultMixin',
-      96128839,
-      $pb.PbFieldType.OS);
-  static final $pb.Extension mixin = $pb.Extension<$core.String>(
-      'google.protobuf.MessageOptions', 'mixin', 96128839, $pb.PbFieldType.OS);
-  static final $pb.Extension overrideGetter = $pb.Extension<$core.bool>(
-      'google.protobuf.FieldOptions',
-      'overrideGetter',
-      28205290,
-      $pb.PbFieldType.OB);
-  static final $pb.Extension overrideSetter = $pb.Extension<$core.bool>(
-      'google.protobuf.FieldOptions',
-      'overrideSetter',
-      28937366,
-      $pb.PbFieldType.OB);
-  static final $pb.Extension overrideHasMethod = $pb.Extension<$core.bool>(
-      'google.protobuf.FieldOptions',
-      'overrideHasMethod',
-      28937461,
-      $pb.PbFieldType.OB);
-  static final $pb.Extension overrideClearMethod = $pb.Extension<$core.bool>(
-      'google.protobuf.FieldOptions',
-      'overrideClearMethod',
-      28907907,
-      $pb.PbFieldType.OB);
-  static final $pb.Extension dartName = $pb.Extension<$core.String>(
-      'google.protobuf.FieldOptions', 'dartName', 28700919, $pb.PbFieldType.OS);
+  static final $pb.Extension<Imports, Imports> imports =
+      $pb.Extension<Imports, Imports>('google.protobuf.FileOptions', 'imports',
+          28125061, $pb.PbFieldType.OM,
+          defaultOrMaker: Imports.getDefault, subBuilder: Imports.create);
+  static final $pb.Extension<$core.String, $core.String> defaultMixin =
+      $pb.Extension<$core.String, $core.String>('google.protobuf.FileOptions',
+          'defaultMixin', 96128839, $pb.PbFieldType.OS);
+  static final $pb.Extension<$core.String, $core.String> mixin =
+      $pb.Extension<$core.String, $core.String>(
+          'google.protobuf.MessageOptions',
+          'mixin',
+          96128839,
+          $pb.PbFieldType.OS);
+  static final $pb.Extension<$core.bool, $core.bool> overrideGetter =
+      $pb.Extension<$core.bool, $core.bool>('google.protobuf.FieldOptions',
+          'overrideGetter', 28205290, $pb.PbFieldType.OB);
+  static final $pb.Extension<$core.bool, $core.bool> overrideSetter =
+      $pb.Extension<$core.bool, $core.bool>('google.protobuf.FieldOptions',
+          'overrideSetter', 28937366, $pb.PbFieldType.OB);
+  static final $pb.Extension<$core.bool, $core.bool> overrideHasMethod =
+      $pb.Extension<$core.bool, $core.bool>('google.protobuf.FieldOptions',
+          'overrideHasMethod', 28937461, $pb.PbFieldType.OB);
+  static final $pb.Extension<$core.bool, $core.bool> overrideClearMethod =
+      $pb.Extension<$core.bool, $core.bool>('google.protobuf.FieldOptions',
+          'overrideClearMethod', 28907907, $pb.PbFieldType.OB);
+  static final $pb.Extension<$core.String, $core.String> dartName =
+      $pb.Extension<$core.String, $core.String>('google.protobuf.FieldOptions',
+          'dartName', 28700919, $pb.PbFieldType.OS);
   static void registerAllExtensions($pb.ExtensionRegistry registry) {
     registry.add(imports);
     registry.add(defaultMixin);
diff --git a/protoc_plugin/lib/src/descriptor.pb.dart b/protoc_plugin/lib/src/descriptor.pb.dart
index cddd9ed47..8efcab926 100644
--- a/protoc_plugin/lib/src/descriptor.pb.dart
+++ b/protoc_plugin/lib/src/descriptor.pb.dart
@@ -3,7 +3,7 @@
 //  source: descriptor.proto
 //
 // @dart = 2.3
-// ignore_for_file: camel_case_types,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
+// ignore_for_file: camel_case_types,unnecessary_const,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
 
 import 'dart:core' as $core;
 
diff --git a/protoc_plugin/lib/src/descriptor.pbenum.dart b/protoc_plugin/lib/src/descriptor.pbenum.dart
index b31a73369..25fcb0bf8 100644
--- a/protoc_plugin/lib/src/descriptor.pbenum.dart
+++ b/protoc_plugin/lib/src/descriptor.pbenum.dart
@@ -3,7 +3,7 @@
 //  source: descriptor.proto
 //
 // @dart = 2.3
-// ignore_for_file: camel_case_types,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
+// ignore_for_file: camel_case_types,unnecessary_const,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
 
 // ignore_for_file: UNDEFINED_SHOWN_NAME,UNUSED_SHOWN_NAME
 import 'dart:core' as $core;
diff --git a/protoc_plugin/lib/src/plugin.pb.dart b/protoc_plugin/lib/src/plugin.pb.dart
index 1c5ce4e9f..03315af68 100644
--- a/protoc_plugin/lib/src/plugin.pb.dart
+++ b/protoc_plugin/lib/src/plugin.pb.dart
@@ -3,7 +3,7 @@
 //  source: plugin.proto
 //
 // @dart = 2.3
-// ignore_for_file: camel_case_types,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
+// ignore_for_file: camel_case_types,unnecessary_const,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type
 
 import 'dart:core' as $core;
 
diff --git a/protoc_plugin/pubspec.yaml b/protoc_plugin/pubspec.yaml
index 3e7130266..b23de7cbe 100644
--- a/protoc_plugin/pubspec.yaml
+++ b/protoc_plugin/pubspec.yaml
@@ -17,3 +17,5 @@ dev_dependencies:
 
 executables:
   protoc-gen-dart: protoc_plugin
+
+dependency_overrides: {protobuf: {path: ../protobuf}}
diff --git a/protoc_plugin/test/repeated_field_test.dart b/protoc_plugin/test/repeated_field_test.dart
index ec036cb7a..42cf837e7 100644
--- a/protoc_plugin/test/repeated_field_test.dart
+++ b/protoc_plugin/test/repeated_field_test.dart
@@ -18,19 +18,19 @@ void main() {
     var msg = TestAllTypes();
     expect(
         (msg.info_.byName["repeatedNestedMessage"]
-                as FieldInfo<TestAllTypes_NestedMessage>)
+                as FieldInfo<TestAllTypes_NestedMessage, List<TestAllTypes_NestedMessage>>)
             .check,
         isNotNull);
 
     expect(
         (msg.info_.byName["repeatedgroup"]
-                as FieldInfo<TestAllTypes_RepeatedGroup>)
+                as FieldInfo<TestAllTypes_RepeatedGroup, List<TestAllTypes_RepeatedGroup>>)
             .check,
         isNotNull);
 
     expect(
         (msg.info_.byName["repeatedNestedEnum"]
-                as FieldInfo<TestAllTypes_NestedEnum>)
+                as FieldInfo<TestAllTypes_NestedEnum, List<TestAllTypes_NestedEnum>>)
             .check,
         isNotNull);
   });