diff --git a/conformance/failure_list_objc.txt b/conformance/failure_list_objc.txt
index e34501ead7..0dd4279587 100644
--- a/conformance/failure_list_objc.txt
+++ b/conformance/failure_list_objc.txt
@@ -1,2 +1,7 @@
 # JSON input or output tests are skipped (in conformance_objc.m) as mobile
 # platforms don't support JSON wire format to avoid code bloat.
+
+Required.Editions_Proto2.ProtobufInput.UnknownOrdering.ProtobufOutput                                              # Unknown field mismatch
+Required.Editions_Proto3.ProtobufInput.UnknownOrdering.ProtobufOutput                                              # Unknown field mismatch
+Required.Proto2.ProtobufInput.UnknownOrdering.ProtobufOutput                                                       # Unknown field mismatch
+Required.Proto3.ProtobufInput.UnknownOrdering.ProtobufOutput                                                       # Unknown field mismatch
diff --git a/objectivec/GPBMessage.m b/objectivec/GPBMessage.m
index 652c791ef0..b0367699dc 100644
--- a/objectivec/GPBMessage.m
+++ b/objectivec/GPBMessage.m
@@ -5,9 +5,9 @@
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 
-#import "GPBMessage.h"
-
 #import <Foundation/Foundation.h>
+#import "GPBMessage_PackagePrivate.h"
+
 #import <objc/message.h>
 #import <objc/runtime.h>
 #import <os/lock.h>
@@ -20,18 +20,11 @@
 #import "GPBDictionary_PackagePrivate.h"
 #import "GPBExtensionInternals.h"
 #import "GPBExtensionRegistry.h"
-#import "GPBMessage_PackagePrivate.h"
 #import "GPBRootObject_PackagePrivate.h"
-#import "GPBUnknownField.h"
-#import "GPBUnknownFieldSet.h"
 #import "GPBUnknownFieldSet_PackagePrivate.h"
 #import "GPBUnknownFields_PackagePrivate.h"
 #import "GPBUtilities_PackagePrivate.h"
 
-// TODO: Consider using on other functions to reduce bloat when
-// some compiler optimizations are enabled.
-#define GPB_NOINLINE __attribute__((noinline))
-
 // Returns a new instance that was automatically created by |autocreator| for
 // its field |field|.
 static GPBMessage *GPBCreateMessageWithAutocreator(Class msgClass, GPBMessage *autocreator,
@@ -71,16 +64,7 @@ NSString *const GPBMessageExceptionMessageTooLarge =
 
 @interface GPBMessage () {
  @package
-  // Only one of these two is ever set, GPBUnknownFieldSet is being deprecated and will
-  // eventually be removed, but because that api support mutation, once the property is
-  // fetch it must continue to be used so any mutations will be honored in future operations
-  // on the message.
-  // Read only operations that access these two/cause things to migration between them should
-  // be protected with an @synchronized(self) block (that way the code also doesn't have to
-  // worry about throws).
-  NSMutableData *unknownFieldData_;
   GPBUnknownFieldSet *unknownFields_;
-
   NSMutableDictionary *extensionMap_;
   // Readonly access to autocreatedExtensionMap_ is protected via readOnlyLock_.
   NSMutableDictionary *autocreatedExtensionMap_;
@@ -119,6 +103,7 @@ static id GetOrCreateMapIvarWithField(GPBMessage *self, GPBFieldDescriptor *fiel
 static id GetMapIvarWithField(GPBMessage *self, GPBFieldDescriptor *field);
 static NSMutableDictionary *CloneExtensionMap(NSDictionary *extensionMap, NSZone *zone)
     __attribute__((ns_returns_retained));
+static GPBUnknownFieldSet *GetOrMakeUnknownFields(GPBMessage *self);
 
 #if defined(DEBUG) && DEBUG
 static NSError *MessageError(NSInteger code, NSDictionary *userInfo) {
@@ -148,178 +133,6 @@ static NSError *ErrorFromException(NSException *exception) {
   return error;
 }
 
-// Helper to encode varints onto the mutable data, the max size need is 10 bytes.
-GPB_NOINLINE
-static uint8_t *EncodeVarintU64(uint64_t val, uint8_t *ptr) {
-  do {
-    uint8_t byte = val & 0x7fU;
-    val >>= 7;
-    if (val) byte |= 0x80U;
-    *(ptr++) = byte;
-  } while (val);
-  return ptr;
-}
-
-// Helper to encode varints onto the mutable data, the max size need is 5 bytes.
-GPB_NOINLINE
-static uint8_t *EncodeVarintU32(uint32_t val, uint8_t *ptr) {
-  do {
-    uint8_t byte = val & 0x7fU;
-    val >>= 7;
-    if (val) byte |= 0x80U;
-    *(ptr++) = byte;
-  } while (val);
-  return ptr;
-}
-
-// Helper to encode signed int32 values as varints onto the mutable data, the max size need is 10
-// bytes.
-GPB_NOINLINE
-static uint8_t *EncodeVarintS32(int32_t val, uint8_t *ptr) {
-  if (val >= 0) {
-    return EncodeVarintU32((uint32_t)val, ptr);
-  } else {
-    // Must sign-extend
-    int64_t extended = val;
-    return EncodeVarintU64((uint64_t)extended, ptr);
-  }
-}
-
-GPB_NOINLINE
-static void AddUnknownFieldVarint32(GPBMessage *self, uint32_t fieldNumber, int32_t value) {
-  if (self->unknownFields_) {
-    [self->unknownFields_ mergeVarintField:fieldNumber value:value];
-    return;
-  }
-  uint8_t buf[20];
-  uint8_t *ptr = buf;
-  ptr = EncodeVarintU32(GPBWireFormatMakeTag(fieldNumber, GPBWireFormatVarint), ptr);
-  ptr = EncodeVarintS32(value, ptr);
-
-  if (self->unknownFieldData_ == nil) {
-    self->unknownFieldData_ = [[NSMutableData alloc] initWithCapacity:ptr - buf];
-    GPBBecomeVisibleToAutocreator(self);
-  }
-  [self->unknownFieldData_ appendBytes:buf length:ptr - buf];
-}
-
-GPB_NOINLINE
-static void AddUnknownFieldLengthDelimited(GPBMessage *self, uint32_t fieldNumber, NSData *value) {
-  if (self->unknownFields_) {
-    [self->unknownFields_ mergeLengthDelimited:fieldNumber value:value];
-    return;
-  }
-  uint8_t buf[20];
-  uint8_t *ptr = buf;
-  ptr = EncodeVarintU32(GPBWireFormatMakeTag(fieldNumber, GPBWireFormatLengthDelimited), ptr);
-  ptr = EncodeVarintU64((uint64_t)value.length, ptr);
-
-  if (self->unknownFieldData_ == nil) {
-    self->unknownFieldData_ = [[NSMutableData alloc] initWithCapacity:(ptr - buf) + value.length];
-    GPBBecomeVisibleToAutocreator(self);
-  }
-  [self->unknownFieldData_ appendBytes:buf length:ptr - buf];
-  [self->unknownFieldData_ appendData:value];
-}
-
-GPB_NOINLINE
-static void AddUnknownMessageSetEntry(GPBMessage *self, uint32_t typeId, NSData *value) {
-  if (self->unknownFields_) {
-    // Legacy Set does this odd storage for MessageSet.
-    [self->unknownFields_ mergeLengthDelimited:typeId value:value];
-    return;
-  }
-
-  uint8_t buf[60];
-  uint8_t *ptr = buf;
-  ptr = EncodeVarintU32(GPBWireFormatMessageSetItemTag, ptr);
-  ptr = EncodeVarintU32(GPBWireFormatMessageSetTypeIdTag, ptr);
-  ptr = EncodeVarintU32(typeId, ptr);
-  ptr = EncodeVarintU32(GPBWireFormatMessageSetMessageTag, ptr);
-  ptr = EncodeVarintU64((uint64_t)value.length, ptr);
-  uint8_t *split = ptr;
-
-  ptr = EncodeVarintU32(GPBWireFormatMessageSetItemEndTag, ptr);
-  uint8_t *end = ptr;
-
-  if (self->unknownFieldData_ == nil) {
-    self->unknownFieldData_ = [[NSMutableData alloc] initWithCapacity:(end - buf) + value.length];
-    GPBBecomeVisibleToAutocreator(self);
-  }
-  [self->unknownFieldData_ appendBytes:buf length:split - buf];
-  [self->unknownFieldData_ appendData:value];
-  [self->unknownFieldData_ appendBytes:split length:end - split];
-}
-
-GPB_NOINLINE
-static void ParseUnknownField(GPBMessage *self, uint32_t tag, GPBCodedInputStream *input) {
-  if (self->unknownFields_) {
-    if (![self->unknownFields_ mergeFieldFrom:tag input:input]) {
-      GPBRaiseStreamError(GPBCodedInputStreamErrorInvalidTag, @"Unexpected end-group tag");
-    }
-    return;
-  }
-
-  uint8_t buf[20];
-  uint8_t *ptr = buf;
-  ptr = EncodeVarintU32(tag, ptr);  // All will need the tag
-  NSData *bytesToAppend = nil;
-
-  GPBCodedInputStreamState *state = &input->state_;
-
-  switch (GPBWireFormatGetTagWireType(tag)) {
-    case GPBWireFormatVarint: {
-      ptr = EncodeVarintU64(GPBCodedInputStreamReadUInt64(state), ptr);
-      break;
-    }
-    case GPBWireFormatFixed64: {
-      uint64_t value = GPBCodedInputStreamReadFixed64(state);
-      *(ptr++) = (uint8_t)(value) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 8) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 16) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 24) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 32) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 40) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 48) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 56) & 0xFF;
-      break;
-    }
-    case GPBWireFormatLengthDelimited: {
-      bytesToAppend = GPBCodedInputStreamReadRetainedBytes(state);
-      ptr = EncodeVarintU64((uint64_t)bytesToAppend.length, ptr);
-      break;
-    }
-    case GPBWireFormatStartGroup: {
-      bytesToAppend = GPBCodedInputStreamReadRetainedBytesToEndGroupNoCopy(
-          state, GPBWireFormatGetTagFieldNumber(tag));
-      break;
-    }
-    case GPBWireFormatEndGroup:
-      GPBRaiseStreamError(GPBCodedInputStreamErrorInvalidTag, @"Unexpected end-group tag");
-      break;
-    case GPBWireFormatFixed32: {
-      uint32_t value = GPBCodedInputStreamReadFixed32(state);
-      *(ptr++) = (uint8_t)(value) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 8) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 16) & 0xFF;
-      *(ptr++) = (uint8_t)(value >> 24) & 0xFF;
-      break;
-    }
-  }
-
-  if (self->unknownFieldData_ == nil) {
-    self->unknownFieldData_ =
-        [[NSMutableData alloc] initWithCapacity:(ptr - buf) + bytesToAppend.length];
-    GPBBecomeVisibleToAutocreator(self);
-  }
-
-  [self->unknownFieldData_ appendBytes:buf length:ptr - buf];
-  if (bytesToAppend) {
-    [self->unknownFieldData_ appendData:bytesToAppend];
-    [bytesToAppend release];
-  }
-}
-
 static void CheckExtension(GPBMessage *self, GPBExtensionDescriptor *extension) {
   if (![self isKindOfClass:extension.containingMessageClass]) {
     [NSException raise:NSInvalidArgumentException
@@ -916,7 +729,8 @@ static void DecodeSingleValueFromInputStream(GPBExtensionDescriptor *extension,
       if (!enumDescriptor.isClosed || enumDescriptor.enumVerifier(val)) {
         nsValue = [[NSNumber alloc] initWithInt:val];
       } else {
-        AddUnknownFieldVarint32(messageToGetExtension, extension->description_->fieldNumber, val);
+        GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(messageToGetExtension);
+        [unknownFields mergeVarintField:extension->description_->fieldNumber value:val];
         nsValue = nil;
       }
       break;
@@ -1106,50 +920,12 @@ void GPBClearMessageAutocreator(GPBMessage *self) {
   self->autocreatorExtension_ = nil;
 }
 
-GPB_NOINLINE
-static void MergeUnknownFieldDataIntoFieldSet(GPBMessage *self, NSData *data,
-                                              GPBUnknownFieldSet *targetSet) {
-  GPBUnknownFieldSet *unknownFields = targetSet ? targetSet : self->unknownFields_;
-
-#if defined(DEBUG) && DEBUG
-  NSCAssert(unknownFields != nil, @"Internal error: unknown fields not initialized.");
-#endif
-
-  BOOL isMessageSet = self.descriptor.isWireFormat;
-  GPBUnknownFieldSet *decodeInto = isMessageSet ? [[GPBUnknownFieldSet alloc] init] : unknownFields;
-
-  GPBCodedInputStream *input = [[GPBCodedInputStream alloc] initWithData:data];
-  @try {
-    [decodeInto mergeFromCodedInputStream:input];
-  } @catch (NSException *exception) {
-#if defined(DEBUG) && DEBUG
-    NSLog(@"%@: Internal exception while parsing the unknown fields into a Set: %@", [self class],
-          exception);
-#endif
-  }
-  [input release];
-
-  if (isMessageSet) {
-    // Need to transform the groups back into how Message feeds the data into a MessageSet when
-    // doing a full MessageSet based decode.
-    GPBUnknownField *groupField = [decodeInto getField:GPBWireFormatMessageSetItem];
-    for (GPBUnknownFieldSet *group in groupField.groupList) {
-      GPBUnknownField *typeIdField = [group getField:GPBWireFormatMessageSetTypeId];
-      GPBUnknownField *messageField = [group getField:GPBWireFormatMessageSetMessage];
-      if (typeIdField.varintList.count != 1 || messageField.lengthDelimitedList.count != 1) {
-#if defined(DEBUG) && DEBUG
-        NSCAssert(NO, @"Internal error: MessageSet group missing typeId or message.");
-#endif
-        continue;
-      }
-      int32_t fieldNumber = (int32_t)[typeIdField.varintList valueAtIndex:0];
-      GPBUnknownField *messageSetField = [[GPBUnknownField alloc] initWithNumber:fieldNumber];
-      [messageSetField addLengthDelimited:messageField.lengthDelimitedList[0]];
-      [unknownFields addField:messageSetField];
-      [messageSetField release];
-    }
-    [decodeInto release];
+static GPBUnknownFieldSet *GetOrMakeUnknownFields(GPBMessage *self) {
+  if (!self->unknownFields_) {
+    self->unknownFields_ = [[GPBUnknownFieldSet alloc] init];
+    GPBBecomeVisibleToAutocreator(self);
   }
+  return self->unknownFields_;
 }
 
 @implementation GPBMessage
@@ -1386,12 +1162,8 @@ static void MergeUnknownFieldDataIntoFieldSet(GPBMessage *self, NSData *data,
   GPBMessage *result = [[descriptor.messageClass allocWithZone:zone] init];
 
   [self copyFieldsInto:result zone:zone descriptor:descriptor];
-
-  @synchronized(self) {
-    result->unknownFields_ = [unknownFields_ copyWithZone:zone];
-    result->unknownFieldData_ = [unknownFieldData_ mutableCopyWithZone:zone];
-  }
-
+  // Make immutable copies of the extra bits.
+  result->unknownFields_ = [unknownFields_ copyWithZone:zone];
   result->extensionMap_ = CloneExtensionMap(extensionMap_, zone);
   return result;
 }
@@ -1465,8 +1237,6 @@ static void MergeUnknownFieldDataIntoFieldSet(GPBMessage *self, NSData *data,
 
   [extensionMap_ release];
   extensionMap_ = nil;
-  [unknownFieldData_ release];
-  unknownFieldData_ = nil;
   [unknownFields_ release];
   unknownFields_ = nil;
 
@@ -1670,20 +1440,11 @@ static void MergeUnknownFieldDataIntoFieldSet(GPBMessage *self, NSData *data,
                               sortedExtensions:sortedExtensions];
     }
   }
-  @synchronized(self) {
-    if (unknownFieldData_) {
-#if defined(DEBUG) && DEBUG
-      NSAssert(unknownFields_ == nil, @"Internal error both unknown states were set");
-#endif
-      [output writeRawData:unknownFieldData_];
-    } else {
-      if (descriptor.isWireFormat) {
-        [unknownFields_ writeAsMessageSetTo:output];
-      } else {
-        [unknownFields_ writeToCodedOutputStream:output];
-      }
-    }
-  }  // @synchronized(self)
+  if (descriptor.isWireFormat) {
+    [unknownFields_ writeAsMessageSetTo:output];
+  } else {
+    [unknownFields_ writeToCodedOutputStream:output];
+  }
 }
 
 - (void)writeDelimitedToOutputStream:(NSOutputStream *)output {
@@ -2404,25 +2165,11 @@ static void MergeUnknownFieldDataIntoFieldSet(GPBMessage *self, NSData *data,
 #pragma mark - Unknown Field Support
 
 - (GPBUnknownFieldSet *)unknownFields {
-  @synchronized(self) {
-    if (unknownFieldData_) {
-#if defined(DEBUG) && DEBUG
-      NSAssert(unknownFields_ == nil, @"Internal error both unknown states were set");
-#endif
-      unknownFields_ = [[GPBUnknownFieldSet alloc] init];
-      MergeUnknownFieldDataIntoFieldSet(self, unknownFieldData_, nil);
-      [unknownFieldData_ release];
-      unknownFieldData_ = nil;
-    }
-    return unknownFields_;
-  }  // @synchronized(self)
+  return unknownFields_;
 }
 
 - (void)setUnknownFields:(GPBUnknownFieldSet *)unknownFields {
-  if (unknownFields != unknownFields_ || unknownFieldData_ != nil) {
-    // Changing sets or clearing.
-    [unknownFieldData_ release];
-    unknownFieldData_ = nil;
+  if (unknownFields != unknownFields_) {
     [unknownFields_ release];
     unknownFields_ = [unknownFields copy];
     GPBBecomeVisibleToAutocreator(self);
@@ -2505,18 +2252,19 @@ static void MergeUnknownFieldDataIntoFieldSet(GPBMessage *self, NSData *data,
   } else {
     // The extension isn't in the registry, but it was well formed, so the whole group structure
     // get preserved as an unknown field.
-
+    GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(self);
     // rawBytes was created via a NoCopy, so it can be reusing a
     // subrange of another NSData that might go out of scope as things
     // unwind, so a copy is needed to ensure what is saved in the
     // unknown fields stays valid.
     NSData *cloned = [NSData dataWithData:rawBytes];
-    AddUnknownMessageSetEntry(self, typeId, cloned);
+    [unknownFields mergeMessageSetMessage:typeId data:cloned];
   }
 }
 
 - (void)addUnknownMapEntry:(int32_t)fieldNum value:(NSData *)data {
-  AddUnknownFieldLengthDelimited(self, fieldNum, data);
+  GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(self);
+  [unknownFields addUnknownMapEntry:fieldNum value:data];
 }
 
 #pragma mark - MergeFromCodedInputStream Support
@@ -2589,7 +2337,8 @@ static void MergeSingleFieldFromCodedInputStream(GPBMessage *self, GPBFieldDescr
       if (!GPBFieldIsClosedEnum(field) || [field isValidEnumValue:val]) {
         GPBSetInt32IvarWithFieldPrivate(self, field, val);
       } else {
-        AddUnknownFieldVarint32(self, GPBFieldNumber(field), val);
+        GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(self);
+        [unknownFields mergeVarintField:GPBFieldNumber(field) value:val];
       }
     }
   }  // switch
@@ -2638,7 +2387,8 @@ static void MergeRepeatedPackedFieldFromCodedInputStream(GPBMessage *self,
         if (!GPBFieldIsClosedEnum(field) || [field isValidEnumValue:val]) {
           [(GPBEnumArray *)genericArray addRawValue:val];
         } else {
-          AddUnknownFieldVarint32(self, GPBFieldNumber(field), val);
+          GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(self);
+          [unknownFields mergeVarintField:GPBFieldNumber(field) value:val];
         }
         break;
       }
@@ -2706,7 +2456,8 @@ static void MergeRepeatedNotPackedFieldFromCodedInputStream(
       if (!GPBFieldIsClosedEnum(field) || [field isValidEnumValue:val]) {
         [(GPBEnumArray *)genericArray addRawValue:val];
       } else {
-        AddUnknownFieldVarint32(self, GPBFieldNumber(field), val);
+        GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(self);
+        [unknownFields mergeVarintField:GPBFieldNumber(field) value:val];
       }
       break;
     }
@@ -2831,7 +2582,11 @@ static void MergeRepeatedNotPackedFieldFromCodedInputStream(
       }
     }
 
-    ParseUnknownField(self, tag, input);
+    GPBUnknownFieldSet *unknownFields = GetOrMakeUnknownFields(self);
+    if (![unknownFields mergeFieldFrom:tag input:input]) {
+      [NSException raise:NSInternalInconsistencyException
+                  format:@"Internal Error: Unable to parse unknown field %u", tag];
+    }
   }  // while(YES)
 }
 
@@ -2953,29 +2708,10 @@ static void MergeRepeatedNotPackedFieldFromCodedInputStream(
   }  // for(fields)
 
   // Unknown fields.
-  if (unknownFields_) {
-#if defined(DEBUG) && DEBUG
-    NSAssert(unknownFieldData_ == nil, @"Internal error both unknown states were set");
-#endif
-    @synchronized(other) {
-      if (other->unknownFields_) {
-#if defined(DEBUG) && DEBUG
-        NSAssert(other->unknownFieldData_ == nil, @"Internal error both unknown states were set");
-#endif
-        [unknownFields_ mergeUnknownFields:other->unknownFields_];
-      } else if (other->unknownFieldData_) {
-        MergeUnknownFieldDataIntoFieldSet(self, other->unknownFieldData_, nil);
-      }
-    }  // @synchronized(other)
+  if (!unknownFields_) {
+    [self setUnknownFields:other.unknownFields];
   } else {
-    NSData *otherData = GPBMessageUnknownFieldsData(other);
-    if (otherData) {
-      if (unknownFieldData_) {
-        [unknownFieldData_ appendData:otherData];
-      } else {
-        unknownFieldData_ = [otherData mutableCopy];
-      }
-    }
+    [unknownFields_ mergeUnknownFields:other.unknownFields];
   }
 
   // Extensions
@@ -3147,72 +2883,15 @@ static void MergeRepeatedNotPackedFieldFromCodedInputStream(
     }
   }
 
-  // Mutation while another thread is doing read only access is invalid, so the only thing we
-  // need to guard against is concurrent r/o access, so we can grab the values (and retain them)
-  // so we have a version to compare against safely incase the second access causes the transform
-  // between internal states.
-  GPBUnknownFieldSet *selfUnknownFields;
-  NSData *selfUnknownFieldData;
-  @synchronized(self) {
-    selfUnknownFields = [unknownFields_ retain];
-    selfUnknownFieldData = [unknownFieldData_ retain];
-  }
-  GPBUnknownFieldSet *otherUnknownFields;
-  NSData *otherUnknownFieldData;
-  @synchronized(otherMsg) {
-    otherUnknownFields = [otherMsg->unknownFields_ retain];
-    otherUnknownFieldData = [otherMsg->unknownFieldData_ retain];
-  }
-#if defined(DEBUG) && DEBUG && !defined(NS_BLOCK_ASSERTIONS)
-  if (selfUnknownFields) {
-    NSAssert(selfUnknownFieldData == nil, @"Internal error both unknown states were set");
-  }
-  if (otherUnknownFields) {
-    NSAssert(otherUnknownFieldData == nil, @"Internal error both unknown states were set");
-  }
-#endif
-  // Since a developer can set the legacy unknownFieldSet, treat nil and empty as the same.
-  if (selfUnknownFields && selfUnknownFields.countOfFields == 0) {
-    [selfUnknownFields release];
-    selfUnknownFields = nil;
-  }
-  if (otherUnknownFields && otherUnknownFields.countOfFields == 0) {
-    [otherUnknownFields release];
-    otherUnknownFields = nil;
-  }
-
-  BOOL result = YES;
-
-  if (selfUnknownFieldData && otherUnknownFieldData) {
-    // Both had data, compare it.
-    result = [selfUnknownFieldData isEqual:otherUnknownFieldData];
-  } else if (selfUnknownFields && otherUnknownFields) {
-    // Both had fields set, compare them.
-    result = [selfUnknownFields isEqual:otherUnknownFields];
-  } else {
-    // At this point, we're done to one have a set/nothing, and the other having data/nothing.
-    GPBUnknownFieldSet *theSet = selfUnknownFields ? selfUnknownFields : otherUnknownFields;
-    NSData *theData = selfUnknownFieldData ? selfUnknownFieldData : otherUnknownFieldData;
-    if (theSet) {
-      if (theData) {
-        GPBUnknownFieldSet *tempSet = [[GPBUnknownFieldSet alloc] init];
-        MergeUnknownFieldDataIntoFieldSet(self, theData, tempSet);
-        result = [tempSet isEqual:theSet];
-        [tempSet release];
-      } else {
-        result = NO;
-      }
-    } else {
-      // It was a data/nothing and nothing, so they equal if the other didn't have data.
-      result = theData == nil;
+  // nil and empty are equal
+  GPBUnknownFieldSet *otherUnknowns = otherMsg->unknownFields_;
+  if ([unknownFields_ countOfFields] != 0 || [otherUnknowns countOfFields] != 0) {
+    if (![unknownFields_ isEqual:otherUnknowns]) {
+      return NO;
     }
   }
 
-  [selfUnknownFields release];
-  [selfUnknownFieldData release];
-  [otherUnknownFields release];
-  [otherUnknownFieldData release];
-  return result;
+  return YES;
 }
 
 // It is very difficult to implement a generic hash for ProtoBuf messages that
@@ -3475,20 +3154,11 @@ static void MergeRepeatedNotPackedFieldFromCodedInputStream(
   }  // for(fields)
 
   // Add any unknown fields.
-  @synchronized(self) {
-    if (unknownFieldData_) {
-#if defined(DEBUG) && DEBUG
-      NSAssert(unknownFields_ == nil, @"Internal error both unknown states were set");
-#endif
-      result += [unknownFieldData_ length];
-    } else {
-      if (descriptor.wireFormat) {
-        result += [unknownFields_ serializedSizeAsMessageSet];
-      } else {
-        result += [unknownFields_ serializedSize];
-      }
-    }
-  }  // @synchronized(self)
+  if (descriptor.wireFormat) {
+    result += [unknownFields_ serializedSizeAsMessageSet];
+  } else {
+    result += [unknownFields_ serializedSize];
+  }
 
   // Add any extensions.
   for (GPBExtensionDescriptor *extension in extensionMap_) {
@@ -4016,29 +3686,20 @@ id GPBGetObjectIvarWithField(GPBMessage *self, GPBFieldDescriptor *field) {
 
 NSData *GPBMessageUnknownFieldsData(GPBMessage *self) {
   NSData *result = nil;
-  @synchronized(self) {
-    GPBUnknownFieldSet *unknownFields = self->unknownFields_;
-    if (unknownFields) {
-#if defined(DEBUG) && DEBUG
-      NSCAssert(self->unknownFieldData_ == nil, @"Internal error both unknown states were set");
-#endif
-      if (self.descriptor.isWireFormat) {
-        NSMutableData *mutableData =
-            [NSMutableData dataWithLength:unknownFields.serializedSizeAsMessageSet];
-        GPBCodedOutputStream *output = [[GPBCodedOutputStream alloc] initWithData:mutableData];
-        [unknownFields writeAsMessageSetTo:output];
-        [output flush];
-        [output release];
-        result = mutableData;
-      } else {
-        result = [unknownFields data];
-      }
+  GPBUnknownFieldSet *unknownFields = self->unknownFields_;
+  if (unknownFields) {
+    if (self.descriptor.isWireFormat) {
+      NSMutableData *mutableData =
+          [NSMutableData dataWithLength:unknownFields.serializedSizeAsMessageSet];
+      GPBCodedOutputStream *output = [[GPBCodedOutputStream alloc] initWithData:mutableData];
+      [unknownFields writeAsMessageSetTo:output];
+      [output flush];
+      [output release];
+      result = mutableData;
     } else {
-      // Internally we can borrow it without a copy since this is immediately used by callers
-      // and multithreaded access with any mutation is not allow on messages.
-      result = self->unknownFieldData_;
+      result = [unknownFields data];
     }
-  }  // @synchronized(self)
+  }
   return result;
 }
 
diff --git a/objectivec/GPBUnknownFieldSet.m b/objectivec/GPBUnknownFieldSet.m
index 6ec70b8925..10fb80c0c7 100644
--- a/objectivec/GPBUnknownFieldSet.m
+++ b/objectivec/GPBUnknownFieldSet.m
@@ -271,11 +271,6 @@ static void GPBUnknownFieldSetMergeUnknownFields(__unused const void *key, const
   [[self mutableFieldForNumber:number create:YES] addVarint:value];
 }
 
-- (void)mergeLengthDelimited:(int32_t)fieldNum value:(NSData *)value {
-  checkNumber(fieldNum);
-  [[self mutableFieldForNumber:fieldNum create:YES] addLengthDelimited:value];
-}
-
 - (BOOL)mergeFieldFrom:(int32_t)tag input:(GPBCodedInputStream *)input {
   NSAssert(GPBWireFormatIsValidTag(tag), @"Got passed an invalid tag");
   int32_t number = GPBWireFormatGetTagFieldNumber(tag);
@@ -318,6 +313,15 @@ static void GPBUnknownFieldSetMergeUnknownFields(__unused const void *key, const
   }
 }
 
+- (void)mergeMessageSetMessage:(int32_t)number data:(NSData *)messageData {
+  [[self mutableFieldForNumber:number create:YES] addLengthDelimited:messageData];
+}
+
+- (void)addUnknownMapEntry:(int32_t)fieldNum value:(NSData *)data {
+  GPBUnknownField *field = [self mutableFieldForNumber:fieldNum create:YES];
+  [field addLengthDelimited:data];
+}
+
 - (void)mergeFromCodedInputStream:(GPBCodedInputStream *)input {
   while (YES) {
     int32_t tag = GPBCodedInputStreamReadTag(&input->state_);
diff --git a/objectivec/GPBUnknownFieldSet_PackagePrivate.h b/objectivec/GPBUnknownFieldSet_PackagePrivate.h
index 1d5ff50f45..7de20ed0cf 100644
--- a/objectivec/GPBUnknownFieldSet_PackagePrivate.h
+++ b/objectivec/GPBUnknownFieldSet_PackagePrivate.h
@@ -27,7 +27,9 @@
 - (void)mergeFromCodedInputStream:(GPBCodedInputStream *)input;
 
 - (void)mergeVarintField:(int32_t)number value:(int32_t)value;
-- (void)mergeLengthDelimited:(int32_t)number value:(NSData *)value;
 - (BOOL)mergeFieldFrom:(int32_t)tag input:(GPBCodedInputStream *)input;
+- (void)mergeMessageSetMessage:(int32_t)number data:(NSData *)messageData;
+
+- (void)addUnknownMapEntry:(int32_t)fieldNum value:(NSData *)data;
 
 @end