diff --git a/protobuf/lib/src/protobuf/protobuf_enum.dart b/protobuf/lib/src/protobuf/protobuf_enum.dart
index b96c119..46c173e 100644
--- a/protobuf/lib/src/protobuf/protobuf_enum.dart
+++ b/protobuf/lib/src/protobuf/protobuf_enum.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// ignore_for_file: non_constant_identifier_names
+
 part of '../../protobuf.dart';
 
 /// A base class for all proto enum types.
@@ -37,12 +39,28 @@
   /// Creates a new constant [ProtobufEnum] using [value] and [name].
   const ProtobufEnum(this.value, this.name);
 
-  /// Creates a Map for all of the [ProtobufEnum]s in [byIndex], mapping each
+  /// This function is for generated code.
+  ///
+  /// Creates a Map for all of the [ProtobufEnum]s in [enumValues], mapping each
   /// [ProtobufEnum]'s [value] to the [ProtobufEnum].
-  static Map<int, T> initByValue<T extends ProtobufEnum>(List<T> byIndex) {
+  ///
+  /// @nodoc
+  static Map<int, T> initByValue<T extends ProtobufEnum>(List<T> enumValues) {
     final byValue = <int, T>{};
-    for (final v in byIndex) {
-      byValue[v.value] = v;
+    for (final enumValue in enumValues) {
+      byValue[enumValue.value] = enumValue;
+    }
+    return byValue;
+  }
+
+  /// This function is for generated code.
+  ///
+  /// @nodoc
+  static List<T?> $_initByValueList<T extends ProtobufEnum>(
+      List<T> enumValues, int maxEnumValue) {
+    final byValue = List<T?>.filled(maxEnumValue + 1, null);
+    for (final enumValue in enumValues) {
+      byValue[enumValue.value] = enumValue;
     }
     return byValue;
   }
diff --git a/protoc_plugin/Makefile b/protoc_plugin/Makefile
index bab82e3..6c04fa5 100644
--- a/protoc_plugin/Makefile
+++ b/protoc_plugin/Makefile
@@ -30,6 +30,7 @@
 	entity \
 	enum_extension \
 	enum_name \
+	enums \
 	extend_unittest \
 	ExtensionEnumNameConflict \
 	ExtensionNameConflict \
diff --git a/protoc_plugin/lib/src/enum_generator.dart b/protoc_plugin/lib/src/enum_generator.dart
index a1cd8b5..287a4fe 100644
--- a/protoc_plugin/lib/src/enum_generator.dart
+++ b/protoc_plugin/lib/src/enum_generator.dart
@@ -175,11 +175,37 @@
       out.println('];');
       out.println();
 
-      out.println(
-          'static final $coreImportPrefix.Map<$coreImportPrefix.int, $classname> _byValue ='
-          ' $protobufImportPrefix.ProtobufEnum.initByValue(values);');
-      out.println('static $classname? valueOf($coreImportPrefix.int value) =>'
-          ' _byValue[value];');
+      var maxEnumValue = -1;
+      for (final valueDescriptor in _canonicalValues) {
+        if (valueDescriptor.number.isNegative) {
+          maxEnumValue = -1; // don't use list
+          break;
+        }
+        if (valueDescriptor.number > maxEnumValue) {
+          maxEnumValue = valueDescriptor.number;
+        }
+      }
+
+      final useList = _canonicalValues.isEmpty ||
+          (maxEnumValue >= 0 &&
+              _canonicalValues.length / (maxEnumValue + 1) >= 0.7);
+
+      if (useList) {
+        out.println(
+            'static final $coreImportPrefix.List<$classname?> _byValue ='
+            ' $protobufImportPrefix.ProtobufEnum.\$_initByValueList(values, $maxEnumValue);');
+
+        out.println('static $classname? valueOf($coreImportPrefix.int value) =>'
+            '  value < 0 || value >= _byValue.length ? null : _byValue[value];');
+      } else {
+        out.println(
+            'static final $coreImportPrefix.Map<$coreImportPrefix.int, $classname> _byValue ='
+            ' $protobufImportPrefix.ProtobufEnum.initByValue(values);');
+
+        out.println('static $classname? valueOf($coreImportPrefix.int value) =>'
+            ' _byValue[value];');
+      }
+
       out.println();
 
       out.println('const $classname._(super.v, super.n);');
diff --git a/protoc_plugin/lib/src/generated/descriptor.pbenum.dart b/protoc_plugin/lib/src/generated/descriptor.pbenum.dart
index dc6f349..15909ed 100644
--- a/protoc_plugin/lib/src/generated/descriptor.pbenum.dart
+++ b/protoc_plugin/lib/src/generated/descriptor.pbenum.dart
@@ -88,9 +88,10 @@
     TYPE_SINT64,
   ];
 
-  static final $core.Map<$core.int, FieldDescriptorProto_Type> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
-  static FieldDescriptorProto_Type? valueOf($core.int value) => _byValue[value];
+  static final $core.List<FieldDescriptorProto_Type?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 18);
+  static FieldDescriptorProto_Type? valueOf($core.int value) =>
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const FieldDescriptorProto_Type._(super.v, super.n);
 }
@@ -111,10 +112,10 @@
     LABEL_REPEATED,
   ];
 
-  static final $core.Map<$core.int, FieldDescriptorProto_Label> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
+  static final $core.List<FieldDescriptorProto_Label?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 3);
   static FieldDescriptorProto_Label? valueOf($core.int value) =>
-      _byValue[value];
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const FieldDescriptorProto_Label._(super.v, super.n);
 }
@@ -137,9 +138,10 @@
     LITE_RUNTIME,
   ];
 
-  static final $core.Map<$core.int, FileOptions_OptimizeMode> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
-  static FileOptions_OptimizeMode? valueOf($core.int value) => _byValue[value];
+  static final $core.List<FileOptions_OptimizeMode?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 3);
+  static FileOptions_OptimizeMode? valueOf($core.int value) =>
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const FileOptions_OptimizeMode._(super.v, super.n);
 }
@@ -159,9 +161,10 @@
     STRING_PIECE,
   ];
 
-  static final $core.Map<$core.int, FieldOptions_CType> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
-  static FieldOptions_CType? valueOf($core.int value) => _byValue[value];
+  static final $core.List<FieldOptions_CType?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 2);
+  static FieldOptions_CType? valueOf($core.int value) =>
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const FieldOptions_CType._(super.v, super.n);
 }
@@ -185,9 +188,10 @@
     JS_NUMBER,
   ];
 
-  static final $core.Map<$core.int, FieldOptions_JSType> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
-  static FieldOptions_JSType? valueOf($core.int value) => _byValue[value];
+  static final $core.List<FieldOptions_JSType?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 2);
+  static FieldOptions_JSType? valueOf($core.int value) =>
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const FieldOptions_JSType._(super.v, super.n);
 }
@@ -212,10 +216,10 @@
     IDEMPOTENT,
   ];
 
-  static final $core.Map<$core.int, MethodOptions_IdempotencyLevel> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
+  static final $core.List<MethodOptions_IdempotencyLevel?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 2);
   static MethodOptions_IdempotencyLevel? valueOf($core.int value) =>
-      _byValue[value];
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const MethodOptions_IdempotencyLevel._(super.v, super.n);
 }
diff --git a/protoc_plugin/lib/src/generated/plugin.pbenum.dart b/protoc_plugin/lib/src/generated/plugin.pbenum.dart
index 399158c..2f427c9 100644
--- a/protoc_plugin/lib/src/generated/plugin.pbenum.dart
+++ b/protoc_plugin/lib/src/generated/plugin.pbenum.dart
@@ -27,10 +27,10 @@
     FEATURE_PROTO3_OPTIONAL,
   ];
 
-  static final $core.Map<$core.int, CodeGeneratorResponse_Feature> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
+  static final $core.List<CodeGeneratorResponse_Feature?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 1);
   static CodeGeneratorResponse_Feature? valueOf($core.int value) =>
-      _byValue[value];
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const CodeGeneratorResponse_Feature._(super.v, super.n);
 }
diff --git a/protoc_plugin/test/generated_message_test.dart b/protoc_plugin/test/generated_message_test.dart
index a25f6a4..63f8f1e 100644
--- a/protoc_plugin/test/generated_message_test.dart
+++ b/protoc_plugin/test/generated_message_test.dart
@@ -10,6 +10,7 @@
 import '../out/protos/constructor_args/google/protobuf/unittest_import.pb.dart'
     as constructor_args_unittest_import;
 import '../out/protos/duplicate_names_import.pb.dart';
+import '../out/protos/enums.pb.dart';
 import '../out/protos/google/protobuf/unittest.pb.dart';
 import '../out/protos/google/protobuf/unittest_import.pb.dart';
 import '../out/protos/google/protobuf/unittest_optimize_for.pb.dart';
@@ -890,4 +891,27 @@
     // constructor arguments, to be able to reuse `assertAllFieldsSet`.
     assertAllFieldsSet(TestAllTypes.fromBuffer(value.writeToBuffer()));
   });
+
+  test('Handling enums defined out of order', () {
+    final message = MessageWithEnums();
+    for (final enum_ in DenseEnum.values) {
+      message.denseEnums.add(enum_);
+    }
+    for (final enum_ in DenseEnumOutOfOrder.values) {
+      message.denseOutOfOrderEnums.add(enum_);
+    }
+    for (final enum_ in SparseEnum.values) {
+      message.sparseEnums.add(enum_);
+    }
+    for (final enum_ in SparseEnumOutOfOrder.values) {
+      message.sparseOutOfOrderEnums.add(enum_);
+    }
+
+    final encoded = message.writeToBuffer();
+    final decoded = MessageWithEnums.fromBuffer(encoded);
+    expect(decoded.denseEnums, DenseEnum.values);
+    expect(decoded.denseOutOfOrderEnums, DenseEnumOutOfOrder.values);
+    expect(decoded.sparseEnums, SparseEnum.values);
+    expect(decoded.sparseOutOfOrderEnums, SparseEnumOutOfOrder.values);
+  });
 }
diff --git a/protoc_plugin/test/goldens/deprecations.pbenum b/protoc_plugin/test/goldens/deprecations.pbenum
index 30bc5d7..c21797e 100644
--- a/protoc_plugin/test/goldens/deprecations.pbenum
+++ b/protoc_plugin/test/goldens/deprecations.pbenum
@@ -24,9 +24,10 @@
     A2,
   ];
 
-  static final $core.Map<$core.int, A> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
-  static A? valueOf($core.int value) => _byValue[value];
+  static final $core.List<A?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 1);
+  static A? valueOf($core.int value) =>
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const A._(super.v, super.n);
 }
diff --git a/protoc_plugin/test/goldens/doc_comments.pbenum b/protoc_plugin/test/goldens/doc_comments.pbenum
index 7cde50e..1a35f24 100644
--- a/protoc_plugin/test/goldens/doc_comments.pbenum
+++ b/protoc_plugin/test/goldens/doc_comments.pbenum
@@ -26,9 +26,10 @@
     A2,
   ];
 
-  static final $core.Map<$core.int, A> _byValue =
-      $pb.ProtobufEnum.initByValue(values);
-  static A? valueOf($core.int value) => _byValue[value];
+  static final $core.List<A?> _byValue =
+      $pb.ProtobufEnum.$_initByValueList(values, 1);
+  static A? valueOf($core.int value) =>
+      value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const A._(super.v, super.n);
 }
diff --git a/protoc_plugin/test/goldens/enum b/protoc_plugin/test/goldens/enum
index 812247d..2dca720 100644
--- a/protoc_plugin/test/goldens/enum
+++ b/protoc_plugin/test/goldens/enum
@@ -11,8 +11,8 @@
     WORK,
   ];
 
-  static final $core.Map<$core.int, PhoneType> _byValue = $pb.ProtobufEnum.initByValue(values);
-  static PhoneType? valueOf($core.int value) => _byValue[value];
+  static final $core.List<PhoneType?> _byValue = $pb.ProtobufEnum.$_initByValueList(values, 2);
+  static PhoneType? valueOf($core.int value) =>  value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const PhoneType._(super.v, super.n);
 }
diff --git a/protoc_plugin/test/goldens/messageGeneratorEnums b/protoc_plugin/test/goldens/messageGeneratorEnums
index 3469c7b..3d673da 100644
--- a/protoc_plugin/test/goldens/messageGeneratorEnums
+++ b/protoc_plugin/test/goldens/messageGeneratorEnums
@@ -11,8 +11,8 @@
     WORK,
   ];
 
-  static final $core.Map<$core.int, PhoneNumber_PhoneType> _byValue = $pb.ProtobufEnum.initByValue(values);
-  static PhoneNumber_PhoneType? valueOf($core.int value) => _byValue[value];
+  static final $core.List<PhoneNumber_PhoneType?> _byValue = $pb.ProtobufEnum.$_initByValueList(values, 2);
+  static PhoneNumber_PhoneType? valueOf($core.int value) =>  value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const PhoneNumber_PhoneType._(super.v, super.n);
 }
diff --git a/protoc_plugin/test/goldens/topLevelEnum.pbenum b/protoc_plugin/test/goldens/topLevelEnum.pbenum
index 30d81a2..69cb70d 100644
--- a/protoc_plugin/test/goldens/topLevelEnum.pbenum
+++ b/protoc_plugin/test/goldens/topLevelEnum.pbenum
@@ -26,8 +26,8 @@
     WORK,
   ];
 
-  static final $core.Map<$core.int, PhoneType> _byValue = $pb.ProtobufEnum.initByValue(values);
-  static PhoneType? valueOf($core.int value) => _byValue[value];
+  static final $core.List<PhoneType?> _byValue = $pb.ProtobufEnum.$_initByValueList(values, 2);
+  static PhoneType? valueOf($core.int value) =>  value < 0 || value >= _byValue.length ? null : _byValue[value];
 
   const PhoneType._(super.v, super.n);
 }
diff --git a/protoc_plugin/test/protos/enums.proto b/protoc_plugin/test/protos/enums.proto
new file mode 100644
index 0000000..03647c9
--- /dev/null
+++ b/protoc_plugin/test/protos/enums.proto
@@ -0,0 +1,54 @@
+enum DenseEnum {
+    DENSE_ENUM_0 = 0;
+    DENSE_ENUM_1 = 1;
+    DENSE_ENUM_2 = 2;
+    DENSE_ENUM_3 = 3;
+    DENSE_ENUM_4 = 4;
+}
+
+enum DenseEnumOutOfOrder {
+    DENSE_ENUM_OOO_0 = 0;
+    DENSE_ENUM_OOO_2 = 2;
+    DENSE_ENUM_OOO_4 = 4;
+    DENSE_ENUM_OOO_3 = 3;
+    DENSE_ENUM_OOO_1 = 1;
+}
+
+enum SparseEnum {
+    SPARSE_ENUM_ZERO = 0;
+    SPARSE_ENUM_MIN_INT = -2147483648;
+    SPARSE_ENUM_1 = -1000000000;
+    SPARSE_ENUM_2 = -100000000;
+    SPARSE_ENUM_3 = -10000000;
+    SPARSE_ENUM_4 = -1000000;
+    SPARSE_ENUM_5 = -100000;
+    SPARSE_ENUM_6 = 100000;
+    SPARSE_ENUM_7 = 1000000;
+    SPARSE_ENUM_8 = 10000000;
+    SPARSE_ENUM_9 = 100000000;
+    SPARSE_ENUM_10 = 1000000000;
+    SPARSE_ENUM_MAX_INT = 2147483647;
+}
+
+enum SparseEnumOutOfOrder {
+    SPARSE_ENUM_OOO_ZERO = 0;
+    SPARSE_ENUM_OOO_1 = -1000000000;
+    SPARSE_ENUM_OOO_MAX_INT = 2147483647;
+    SPARSE_ENUM_OOO_4 = -1000000;
+    SPARSE_ENUM_OOO_6 = 100000;
+    SPARSE_ENUM_OOO_MIN_INT = -2147483648;
+    SPARSE_ENUM_OOO_7 = 1000000;
+    SPARSE_ENUM_OOO_5 = -100000;
+    SPARSE_ENUM_OOO_8 = 10000000;
+    SPARSE_ENUM_OOO_3 = -10000000;
+    SPARSE_ENUM_OOO_10 = 1000000000;
+    SPARSE_ENUM_OOO_2 = -100000000;
+    SPARSE_ENUM_OOO_9 = 100000000;
+}
+
+message MessageWithEnums {
+    repeated DenseEnum denseEnums = 1;
+    repeated DenseEnumOutOfOrder denseOutOfOrderEnums = 2;
+    repeated SparseEnum sparseEnums = 3;
+    repeated SparseEnumOutOfOrder sparseOutOfOrderEnums = 4;
+}