diff --git a/protobuf/lib/src/protobuf/coded_buffer_reader.dart b/protobuf/lib/src/protobuf/coded_buffer_reader.dart
index cc7e3ddf1..5da7dae0a 100644
--- a/protobuf/lib/src/protobuf/coded_buffer_reader.dart
+++ b/protobuf/lib/src/protobuf/coded_buffer_reader.dart
@@ -26,11 +26,10 @@ class CodedBufferReader {
   final int _sizeLimit;
 
   CodedBufferReader(List<int> buffer,
-      {int recursionLimit = DEFAULT_RECURSION_LIMIT,
-      int sizeLimit = DEFAULT_SIZE_LIMIT})
+      {int recursionLimit = DEFAULT_RECURSION_LIMIT, int? sizeLimit})
       : _buffer = buffer is Uint8List ? buffer : Uint8List.fromList(buffer),
         _recursionLimit = recursionLimit,
-        _sizeLimit = math.min(sizeLimit, buffer.length) {
+        _sizeLimit = math.min(sizeLimit ?? DEFAULT_SIZE_LIMIT, buffer.length) {
     _currentLimit = _sizeLimit;
   }
 
diff --git a/protobuf/lib/src/protobuf/generated_message.dart b/protobuf/lib/src/protobuf/generated_message.dart
index d34dac4ad..370d848d3 100644
--- a/protobuf/lib/src/protobuf/generated_message.dart
+++ b/protobuf/lib/src/protobuf/generated_message.dart
@@ -198,9 +198,12 @@ abstract class GeneratedMessage {
   /// * Else, if it's a scalar, this overwrites our field.
   /// * Else, (it's a non-repeated sub-message), this recursively merges into
   ///   the existing sub-message.
-  void mergeFromBuffer(List<int> input,
-      [ExtensionRegistry extensionRegistry = ExtensionRegistry.EMPTY]) {
-    final codedInput = CodedBufferReader(input);
+  void mergeFromBuffer(
+    List<int> input, [
+    ExtensionRegistry extensionRegistry = ExtensionRegistry.EMPTY,
+    int? sizeLimit,
+  ]) {
+    final codedInput = CodedBufferReader(input, sizeLimit: sizeLimit);
     final meta = _fieldSet._meta;
     _mergeFromCodedBufferReader(meta, _fieldSet, codedInput, extensionRegistry);
     codedInput.checkLastTagWas(0);