@@ -229,12 +229,13 @@
 	if (_diskNumber == 0xFFFF ||
 	    _centralDirectoryDisk == 0xFFFF ||
 	    _centralDirectoryEntriesInDisk == 0xFFFF ||
 	    _centralDirectoryEntries == 0xFFFF ||
 	    _centralDirectorySize == 0xFFFFFFFF ||
-	    _centralDirectoryOffset == 0xFFFFFFFF) {
-		uint64_t offset64, size;
+	    _centralDirectoryOffset == -1) {
+		int64_t offset64;
+		uint64_t size;
 
 		seekOrThrowInvalidFormat(_stream, offset - 20, SEEK_END);
 
 		if ([_stream readLittleEndianInt32] != 0x07064B50) {
 			objc_autoreleasePoolPop(pool);
@@ -246,11 +247,11 @@
 		 * central directory record.
 		 */
 		[_stream readLittleEndianInt32];
 		offset64 = [_stream readLittleEndianInt64];
 
-		if ((of_offset_t)offset64 != offset64)
+		if (offset64 < 0 || (of_offset_t)offset64 != offset64)
 			@throw [OFOutOfRangeException exception];
 
 		seekOrThrowInvalidFormat(_stream,
 		    (of_offset_t)offset64, SEEK_SET);
 
@@ -272,11 +273,12 @@
 		    [_stream readLittleEndianInt64];
 		_centralDirectoryEntries = [_stream readLittleEndianInt64];
 		_centralDirectorySize = [_stream readLittleEndianInt64];
 		_centralDirectoryOffset = [_stream readLittleEndianInt64];
 
-		if ((of_offset_t)_centralDirectoryOffset !=
+		if (_centralDirectoryOffset < 0 ||
+		    (of_offset_t)_centralDirectoryOffset !=
 		    _centralDirectoryOffset)
 			@throw [OFOutOfRangeException exception];
 	}
 
 	objc_autoreleasePoolPop(pool);
@@ -284,11 +286,12 @@
 
 - (void)OF_readEntries
 {
 	void *pool = objc_autoreleasePoolPush();
 
-	if ((of_offset_t)_centralDirectoryOffset != _centralDirectoryOffset)
+	if (_centralDirectoryOffset < 0 ||
+	    (of_offset_t)_centralDirectoryOffset != _centralDirectoryOffset)
 		@throw [OFOutOfRangeException exception];
 
 	seekOrThrowInvalidFormat(_stream,
 	    (of_offset_t)_centralDirectoryOffset, SEEK_SET);
 
@@ -321,11 +324,11 @@
 - (OFStream*)streamForReadingFile: (OFString*)path
 {
 	void *pool = objc_autoreleasePoolPush();
 	OFZIPArchiveEntry *entry = [_pathToEntryMap objectForKey: path];
 	OFZIPArchive_LocalFileHeader *localFileHeader;
-	uint64_t offset64;
+	int64_t offset64;
 
 	if (entry == nil)
 		@throw [OFOpenItemFailedException exceptionWithPath: path
 							       mode: @"rb"
 							      errNo: ENOENT];
@@ -333,11 +336,11 @@
 	[_lastReturnedStream close];
 	[_lastReturnedStream release];
 	_lastReturnedStream = nil;
 
 	offset64 = [entry OF_localFileHeaderOffset];
-	if ((of_offset_t)offset64 != offset64)
+	if (offset64 < 0 || (of_offset_t)offset64 != offset64)
 		@throw [OFOutOfRangeException exception];
 
 	seekOrThrowInvalidFormat(_stream, (of_offset_t)offset64, SEEK_SET);
 	localFileHeader = [[[OFZIPArchive_LocalFileHeader alloc]
 	    initWithStream: _stream] autorelease];