diff --git a/protobuf/CHANGELOG.md b/protobuf/CHANGELOG.md
index c88b6e9..b2c0c07 100644
--- a/protobuf/CHANGELOG.md
+++ b/protobuf/CHANGELOG.md
@@ -3,6 +3,7 @@
 * Fix hashcode of bytes fields.
 * Fix issue with the `permissiveEnums` option to `mergeFromProto3Json`.
   The comparison did not work properly.
+* Fix binary representation of negative int32 values.
 
 ## 1.0.1
 
diff --git a/protobuf/lib/src/protobuf/coded_buffer_writer.dart b/protobuf/lib/src/protobuf/coded_buffer_writer.dart
index c5c60a5..e4f6781 100644
--- a/protobuf/lib/src/protobuf/coded_buffer_writer.dart
+++ b/protobuf/lib/src/protobuf/coded_buffer_writer.dart
@@ -353,7 +353,7 @@
         value.writeToCodedBufferWriter(this);
         break;
       case PbFieldType._INT32_BIT:
-        _writeVarint32(value & 0xffffffff);
+        _writeVarint64(Int64(value));
         break;
       case PbFieldType._INT64_BIT:
         _writeVarint64(value);
diff --git a/protobuf/test/codec_test.dart b/protobuf/test/codec_test.dart
index f1ee083..5b71aff 100755
--- a/protobuf/test/codec_test.dart
+++ b/protobuf/test/codec_test.dart
@@ -32,13 +32,6 @@
 
   final int32ToBytes = convertToBytes(PbFieldType.O3);
 
-  test('testEquivalentBitwiseRepresentations', () {
-    final uint32ToBytes = convertToBytes(PbFieldType.OU3);
-    // Internal representation appears to be bit-wise identical
-    // an additional internal flag must differentiate.
-    expect(int32ToBytes(-1), uint32ToBytes(4294967295));
-  });
-
   test('testInt32RoundTrips', () {
     final roundtrip = roundtripTester(
         fromBytes: (CodedBufferReader reader) => reader.readInt32(),
@@ -48,9 +41,10 @@
     roundtrip(206, [0xce, 0x01]);
     roundtrip(300, [0xac, 0x02]);
     roundtrip(2147483647, [0xff, 0xff, 0xff, 0xff, 0x07]);
-    roundtrip(-2147483648, [0x80, 0x80, 0x80, 0x80, 0x08]);
-    roundtrip(-1, [0xff, 0xff, 0xff, 0xff, 0x0f]);
-    roundtrip(-2, [0xfe, 0xff, 0xff, 0xff, 0x0f]);
+    roundtrip(-2147483648,
+        [0x80, 0x80, 0x80, 0x80, 0xf8, 0xff, 0xff, 0xff, 0xff, 0x01]);
+    roundtrip(-1, [0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01]);
+    roundtrip(-2, [0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01]);
   });
 
   test('testSint32', () {