diff --git a/protobuf/CHANGELOG.md b/protobuf/CHANGELOG.md
index 3a41a329..9d5c038a 100644
--- a/protobuf/CHANGELOG.md
+++ b/protobuf/CHANGELOG.md
@@ -16,10 +16,17 @@
 * Fix `PbList` methods `addAll`, `insertAll`, `replaceRange`, `setAll`,
   `setRange` iterating the `Iterable` argument twice. ([#730], [#1070])
 
+* Fix `GeneratedMessage.==` throwing a type error when comparing `map` fields in
+  some cases. ([#1075], [#1077])
+
+  This bug was introduced with protobuf-5.0.0.
+
 [#1060]: https://github.com/google/protobuf.dart/pull/1060
 [#1062]: https://github.com/google/protobuf.dart/pull/1062
 [#730]: https://github.com/google/protobuf.dart/issues/730
 [#1070]: https://github.com/google/protobuf.dart/pull/1070
+[#1075]: https://github.com/google/protobuf.dart/issues/1075
+[#1077]: https://github.com/google/protobuf.dart/pull/1077
 
 ## 5.0.0
 
diff --git a/protobuf/lib/src/protobuf/utils.dart b/protobuf/lib/src/protobuf/utils.dart
index 7de5c1e7..3a4db970 100644
--- a/protobuf/lib/src/protobuf/utils.dart
+++ b/protobuf/lib/src/protobuf/utils.dart
@@ -8,7 +8,7 @@ import 'internal.dart';
 import 'json_parsing_context.dart';
 
 // TODO(antonm): reconsider later if PbList should take care of equality.
-bool deepEquals(Object lhs, Object rhs) {
+bool deepEquals(Object? lhs, Object? rhs) {
   // Some GeneratedMessages implement Map, so test this first.
   if (lhs is GeneratedMessage) return lhs == rhs;
   if (rhs is GeneratedMessage) return false;
@@ -17,7 +17,7 @@ bool deepEquals(Object lhs, Object rhs) {
   return lhs == rhs;
 }
 
-bool areListsEqual(List lhs, List rhs) {
+bool areListsEqual(List<Object?> lhs, List<Object?> rhs) {
   if (lhs.length != rhs.length) return false;
   for (var i = 0; i < lhs.length; i++) {
     if (!deepEquals(lhs[i], rhs[i])) return false;
@@ -25,7 +25,7 @@ bool areListsEqual(List lhs, List rhs) {
   return true;
 }
 
-bool areMapsEqual(Map lhs, Map rhs) {
+bool areMapsEqual(Map<Object?, Object?> lhs, Map<Object?, Object?> rhs) {
   if (lhs.length != rhs.length) return false;
   return lhs.keys.every((key) => deepEquals(lhs[key], rhs[key]));
 }
diff --git a/protoc_plugin/test/map_test.dart b/protoc_plugin/test/map_test.dart
index 3002324b..e437948a 100644
--- a/protoc_plugin/test/map_test.dart
+++ b/protoc_plugin/test/map_test.dart
@@ -7,6 +7,7 @@ import 'package:test/test.dart'
 
 import 'gen/map_api.pb.dart' as pb;
 import 'gen/map_api2.pb.dart' as pb2;
+import 'gen/map_field.pb.dart';
 
 void main() {
   test("message doesn't implement Map when turned off", () {
@@ -157,4 +158,23 @@ void main() {
       });
     }, throwsArgumentError);
   });
+
+  test(
+    "Map equality check handles missing keys without type errors, bug #1075",
+    () {
+      final message1 = TestMap();
+      final message2 = TestMap();
+      expect(message1, message2);
+
+      message1.int32ToInt32Field[1] = 2;
+      expect(message1 == message2, false);
+
+      message2.int32ToInt32Field[3] = 4;
+      expect(message1 == message2, false);
+
+      message1.int32ToInt32Field[3] = 4;
+      message2.int32ToInt32Field[1] = 2;
+      expect(message1, message2);
+    },
+  );
 }