diff --git a/protobuf/CHANGELOG.md b/protobuf/CHANGELOG.md
index f1cd835f3..1bae5efe8 100644
--- a/protobuf/CHANGELOG.md
+++ b/protobuf/CHANGELOG.md
@@ -1,3 +1,13 @@
+## 1.0.2
+
+* Fixed generic handling of unknown fields.
+  * `GeneratedMessage.clearField(tagNumber)` will now also clear an unknown
+    field.
+  * `GeneratedMessage.hasField(tagNumber)` will now return true if there is an
+  unknown field.
+* Handle cases where a field that is part of a oneof is removed by the
+  protobuf aware treeshaker.
+
 ## 1.0.1
 
 * Fix issue with `ExtensionRegistry.reparseMessage` not handling map fields with
diff --git a/protobuf/lib/src/protobuf/coded_buffer.dart b/protobuf/lib/src/protobuf/coded_buffer.dart
index b7cd01603..0788c5ce1 100644
--- a/protobuf/lib/src/protobuf/coded_buffer.dart
+++ b/protobuf/lib/src/protobuf/coded_buffer.dart
@@ -42,6 +42,7 @@ void _mergeFromCodedBufferReader(
     }
 
     if (fi == null || !_wireTypeMatches(fi.type, wireType)) {
+      fs._updateOneOfCase(tagNumber);
       if (!fs._ensureUnknownFields().mergeFieldFromBuffer(tag, input)) {
         return;
       }
diff --git a/protobuf/lib/src/protobuf/field_set.dart b/protobuf/lib/src/protobuf/field_set.dart
index 04256f124..3f7b50d16 100644
--- a/protobuf/lib/src/protobuf/field_set.dart
+++ b/protobuf/lib/src/protobuf/field_set.dart
@@ -236,24 +236,23 @@ class _FieldSet {
   bool _hasField(int tagNumber) {
     var fi = _nonExtensionInfo(tagNumber);
     if (fi != null) return _$has(fi.index);
+    if (_hasUnknownFields && _unknownFields.hasField(tagNumber)) {
+      return true;
+    }
     if (!_hasExtensions) return false;
     return _extensions._hasField(tagNumber);
   }
 
   void _clearField(int tagNumber) {
     _ensureWritable();
+    int oneofIndex = _meta.oneofs[tagNumber];
+    if (oneofIndex != null) _oneofCases.remove(oneofIndex);
+
     var fi = _nonExtensionInfo(tagNumber);
     if (fi != null) {
       // clear a non-extension field
       if (_hasObservers) _eventPlugin.beforeClearField(fi);
       _values[fi.index] = null;
-
-      if (_meta.oneofs.containsKey(fi.tagNumber)) {
-        _oneofCases.remove(_meta.oneofs[fi.tagNumber]);
-      }
-
-      int oneofIndex = _meta.oneofs[fi.tagNumber];
-      if (oneofIndex != null) _oneofCases[oneofIndex] = 0;
       return;
     }
 
@@ -265,8 +264,9 @@ class _FieldSet {
       }
     }
 
-    // neither a regular field nor an extension.
-    // TODO(skybrian) throw?
+    if (_hasUnknownFields) {
+      _unknownFields._clearField(tagNumber);
+    }
   }
 
   /// Sets a non-repeated field with error-checking.
@@ -342,14 +342,18 @@ class _FieldSet {
     return newValue;
   }
 
-  /// Sets a non-extended field and fires events.
-  void _setNonExtensionFieldUnchecked(FieldInfo fi, value) {
-    int tag = fi.tagNumber;
-    int oneofIndex = _meta.oneofs[tag];
+  void _updateOneOfCase(int newTagnumber) {
+    int oneofIndex = _meta.oneofs[newTagnumber];
     if (oneofIndex != null) {
-      _clearField(_oneofCases[oneofIndex]);
-      _oneofCases[oneofIndex] = tag;
+      final currentTagnumber = _oneofCases[oneofIndex];
+      if (currentTagnumber != null) _clearField(currentTagnumber);
+      _oneofCases[oneofIndex] = newTagnumber;
     }
+  }
+
+  /// Sets a non-extended field and fires events.
+  void _setNonExtensionFieldUnchecked(FieldInfo fi, value) {
+    _updateOneOfCase(fi.tagNumber);
 
     // It is important that the callback to the observers is not moved to the
     // beginning of this method but happens just before the value is set.
@@ -498,13 +502,7 @@ class _FieldSet {
     if (_hasObservers) {
       _eventPlugin.beforeSetField(_nonExtensionInfoByIndex(index), value);
     }
-    int tag = _meta.byIndex[index].tagNumber;
-    int oneofIndex = _meta.oneofs[tag];
-
-    if (oneofIndex != null) {
-      _clearField(_oneofCases[oneofIndex]);
-      _oneofCases[oneofIndex] = tag;
-    }
+    _updateOneOfCase(_meta.byIndex[index].tagNumber);
     _values[index] = value;
   }
 
@@ -713,7 +711,12 @@ class _FieldSet {
     }
 
     if (other._hasUnknownFields) {
-      _ensureUnknownFields().mergeFromUnknownFieldSet(other._unknownFields);
+      final unknownFieldSet = _ensureUnknownFields();
+      final otherUnknownFieldSet = other._unknownFields;
+      otherUnknownFieldSet._fields.forEach((key, value) {
+        _updateOneOfCase(key);
+        unknownFieldSet.mergeField(key, value);
+      });
     }
   }
 
diff --git a/protobuf/lib/src/protobuf/generated_message.dart b/protobuf/lib/src/protobuf/generated_message.dart
index 09445693c..9659cf235 100644
--- a/protobuf/lib/src/protobuf/generated_message.dart
+++ b/protobuf/lib/src/protobuf/generated_message.dart
@@ -300,8 +300,11 @@ abstract class GeneratedMessage {
 
   /// Clears the contents of a given field.
   ///
-  /// If it's an extension field, the Extension will be kept.
-  /// The tagNumber should be a valid tag or extension.
+  /// If it's an extension field, the value will be removed, but the Extension
+  /// will be kept.
+  ///
+  /// If the tagNumber is present as an unknown field, that field will be
+  /// removed.
   void clearField(int tagNumber) => _fieldSet._clearField(tagNumber);
 
   int $_whichOneof(int oneofIndex) => _fieldSet._oneofCases[oneofIndex] ?? 0;
@@ -355,6 +358,8 @@ abstract class GeneratedMessage {
       _fieldSet._extensions._getFieldOrNull(extension) != null;
 
   /// Returns [:true:] if this message has a field associated with [tagNumber].
+  ///
+  /// Will return [:true:] even if that field is an unknown field.
   bool hasField(int tagNumber) => _fieldSet._hasField(tagNumber);
 
   /// Merges the contents of the [other] into this message.
diff --git a/protobuf/lib/src/protobuf/unknown_field_set.dart b/protobuf/lib/src/protobuf/unknown_field_set.dart
index a136f36de..5488491d4 100644
--- a/protobuf/lib/src/protobuf/unknown_field_set.dart
+++ b/protobuf/lib/src/protobuf/unknown_field_set.dart
@@ -31,8 +31,15 @@ class UnknownFieldSet {
 
   UnknownFieldSetField getField(int tagNumber) => _fields[tagNumber];
 
+  /// Returns `true` if [tagNumber] is set in [this].
   bool hasField(int tagNumber) => _fields.containsKey(tagNumber);
 
+  /// Removes [tagNumber] from [this].
+  ///
+  /// Does nothing if [tagNumber] is unset.
+  void _clearField(int tagNumber) => _fields.remove(tagNumber);
+
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void addField(int number, UnknownFieldSetField field) {
     _ensureWritable('addField');
     _checkFieldNumber(number);
@@ -49,6 +56,10 @@ class UnknownFieldSet {
       ..groups.addAll(field.groups);
   }
 
+  /// Merges the field following [tag] into [this].
+  ///
+  /// Returns `false` if the tag is the end of a group. `true` otherwise.
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   bool mergeFieldFromBuffer(int tag, CodedBufferReader input) {
     _ensureWritable('mergeFieldFromBuffer');
     int number = getTagFieldNumber(tag);
@@ -76,6 +87,7 @@ class UnknownFieldSet {
     }
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeFromCodedBufferReader(CodedBufferReader input) {
     _ensureWritable('mergeFromCodedBufferReader');
     while (true) {
@@ -86,6 +98,7 @@ class UnknownFieldSet {
     }
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeFromUnknownFieldSet(UnknownFieldSet other) {
     _ensureWritable('mergeFromUnknownFieldSet');
     for (int key in other._fields.keys) {
@@ -99,26 +112,31 @@ class UnknownFieldSet {
     }
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeFixed32Field(int number, int value) {
     _ensureWritable('mergeFixed32Field');
     _getField(number).addFixed32(value);
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeFixed64Field(int number, Int64 value) {
     _ensureWritable('mergeFixed64Field');
     _getField(number).addFixed64(value);
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeGroupField(int number, UnknownFieldSet value) {
     _ensureWritable('mergeGroupField');
     _getField(number).addGroup(value);
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeLengthDelimitedField(int number, List<int> value) {
     _ensureWritable('mergeLengthDelimitedField');
     _getField(number).addLengthDelimited(value);
   }
 
+  // TODO(sigurdm): Does not update oneofs. Consider deprecating.
   void mergeVarintField(int number, Int64 value) {
     _ensureWritable('mergeVarintField');
     _getField(number).addVarint(value);
diff --git a/protobuf/pubspec.yaml b/protobuf/pubspec.yaml
index ad484aaf1..4ad688c2b 100644
--- a/protobuf/pubspec.yaml
+++ b/protobuf/pubspec.yaml
@@ -1,6 +1,6 @@
 name: protobuf
-version: 1.0.1
-description: >
+version: 1.0.2
+description:
   Runtime library for protocol buffers support.
   Use https://pub.dartlang.org/packages/protoc_plugin to generate dart code for your '.proto' files.
 homepage: https://github.com/dart-lang/protobuf
diff --git a/protoc_plugin/test/unknown_field_set_test.dart b/protoc_plugin/test/unknown_field_set_test.dart
index 2971df5c4..324cc184d 100755
--- a/protoc_plugin/test/unknown_field_set_test.dart
+++ b/protoc_plugin/test/unknown_field_set_test.dart
@@ -330,4 +330,9 @@ void main() {
 
     _checkNotEqual(f1, f2);
   });
+
+  test('GeneratedMessage.hasField sees unknown fields', () {
+    expect(emptyMessage.hasField(testAllTypes.getTagNumber('optionalInt32')),
+        true);
+  });
 }