diff --git a/objectivec/GPBUnknownFieldSet_PackagePrivate.h b/objectivec/GPBUnknownFieldSet_PackagePrivate.h
new file mode 100644
index 0000000..e27127a
--- /dev/null
+++ b/objectivec/GPBUnknownFieldSet_PackagePrivate.h
@@ -0,0 +1,61 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#import <Foundation/Foundation.h>
+
+#import "GPBUnknownFieldSet.h"
+
+@class GPBCodedOutputStream;
+@class GPBCodedInputStream;
+
+@interface GPBUnknownFieldSet ()
+
++ (BOOL)isFieldTag:(int32_t)tag;
+
+- (NSData *)data;
+
+- (size_t)serializedSize;
+- (size_t)serializedSizeAsMessageSet;
+
+- (void)writeToCodedOutputStream:(GPBCodedOutputStream *)output;
+- (void)writeAsMessageSetTo:(GPBCodedOutputStream *)output;
+
+- (void)mergeUnknownFields:(GPBUnknownFieldSet *)other;
+
+- (void)mergeFromCodedInputStream:(GPBCodedInputStream *)input;
+- (void)mergeFromData:(NSData *)data;
+
+- (void)mergeVarintField:(int32_t)number value:(int32_t)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