Index: src/OFIntrospection.m
==================================================================
--- src/OFIntrospection.m
+++ src/OFIntrospection.m
@@ -369,11 +369,14 @@
 - (instancetype)of_initWithIvar: (struct objc_ivar *)ivar
 {
 	self = [super init];
 
 	@try {
-		_name = [[OFString alloc] initWithUTF8String: ivar->name];
+		if (ivar->name != NULL)
+			_name = [[OFString alloc]
+			    initWithUTF8String: ivar->name];
+
 		_typeEncoding = ivar->type;
 		_offset = ivar->offset;
 	} @catch (id e) {
 		[self release];
 		@throw e;
@@ -388,12 +391,12 @@
 
 	@try {
 		const char *name = ivar_getName(ivar);
 
 		if (name != NULL)
-			_name = [[OFString alloc] initWithUTF8String:
-			    ivar_getName(ivar)];
+			_name = [[OFString alloc] initWithUTF8String: name];
+
 		_typeEncoding = ivar_getTypeEncoding(ivar);
 		_offset = ivar_getOffset(ivar);
 	} @catch (id e) {
 		[self release];
 		@throw e;

Index: src/OFMutableTarArchiveEntry.h
==================================================================
--- src/OFMutableTarArchiveEntry.h
+++ src/OFMutableTarArchiveEntry.h
@@ -32,21 +32,21 @@
 @property (readwrite, copy, nonatomic) OFString *fileName;
 
 /*!
  * The mode of the entry.
  */
-@property (readwrite, nonatomic) uint16_t mode;
+@property (readwrite, nonatomic) uint32_t mode;
 
 /*!
  * The UID of the owner.
  */
-@property (readwrite, nonatomic) uint16_t UID;
+@property (readwrite, nonatomic) uint32_t UID;
 
 /*!
  * The GID of the group.
  */
-@property (readwrite, nonatomic) uint16_t GID;
+@property (readwrite, nonatomic) uint32_t GID;
 
 /*!
  * The size of the file.
  */
 @property (readwrite, nonatomic) uint64_t size;

Index: src/OFMutableTarArchiveEntry.m
==================================================================
--- src/OFMutableTarArchiveEntry.m
+++ src/OFMutableTarArchiveEntry.m
@@ -38,21 +38,21 @@
 	OFString *old = _fileName;
 	_fileName = [fileName copy];
 	[old release];
 }
 
-- (void)setMode: (uint16_t)mode
+- (void)setMode: (uint32_t)mode
 {
 	_mode = mode;
 }
 
-- (void)setUID: (uint16_t)UID
+- (void)setUID: (uint32_t)UID
 {
 	_UID = UID;
 }
 
-- (void)setGID: (uint16_t)GID
+- (void)setGID: (uint32_t)GID
 {
 	_GID = GID;
 }
 
 - (void)setSize: (uint64_t)size

Index: src/OFTarArchive.m
==================================================================
--- src/OFTarArchive.m
+++ src/OFTarArchive.m
@@ -157,11 +157,11 @@
 
 - (OFTarArchiveEntry *)nextEntry
 {
 	OFTarArchiveEntry *entry;
 	union {
-		char c[512];
+		unsigned char c[512];
 		uint32_t u32[512 / sizeof(uint32_t)];
 	} buffer;
 	bool empty = true;
 
 	if (_mode != OF_TAR_ARCHIVE_MODE_READ)

Index: src/OFTarArchiveEntry+Private.h
==================================================================
--- src/OFTarArchiveEntry+Private.h
+++ src/OFTarArchiveEntry+Private.h
@@ -19,11 +19,11 @@
 OF_ASSUME_NONNULL_BEGIN
 
 @class OFStream;
 
 @interface OFTarArchiveEntry ()
-- (instancetype)of_initWithHeader: (char [_Nonnull 512])header
+- (instancetype)of_initWithHeader: (unsigned char [_Nonnull 512])header
     OF_METHOD_FAMILY(init);
 - (void)of_writeToStream: (OFStream *)stream;
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/OFTarArchiveEntry.h
==================================================================
--- src/OFTarArchiveEntry.h
+++ src/OFTarArchiveEntry.h
@@ -48,13 +48,13 @@
  * @brief A class which represents an entry of a tar archive.
  */
 @interface OFTarArchiveEntry: OFObject <OFCopying, OFMutableCopying>
 {
 	OFString *_fileName;
-	uint16_t _mode;
+	uint32_t _mode;
 	uint64_t _size;
-	uint16_t _UID, _GID;
+	uint32_t _UID, _GID;
 	OFDate *_modificationDate;
 	of_tar_archive_entry_type_t _type;
 	OFString *_Nullable _targetFileName;
 	OFString *_Nullable _owner, *_Nullable _group;
 	uint32_t _deviceMajor, _deviceMinor;
@@ -66,21 +66,21 @@
 @property (readonly, copy, nonatomic) OFString *fileName;
 
 /*!
  * The mode of the entry.
  */
-@property (readonly, nonatomic) uint16_t mode;
+@property (readonly, nonatomic) uint32_t mode;
 
 /*!
  * The UID of the owner.
  */
-@property (readonly, nonatomic) uint16_t UID;
+@property (readonly, nonatomic) uint32_t UID;
 
 /*!
  * The GID of the group.
  */
-@property (readonly, nonatomic) uint16_t GID;
+@property (readonly, nonatomic) uint32_t GID;
 
 /*!
  * The size of the file.
  */
 @property (readonly, nonatomic) uint64_t size;

Index: src/OFTarArchiveEntry.m
==================================================================
--- src/OFTarArchiveEntry.m
+++ src/OFTarArchiveEntry.m
@@ -24,17 +24,17 @@
 #import "OFDate.h"
 
 #import "OFOutOfRangeException.h"
 
 static OFString *
-stringFromBuffer(const char *buffer, size_t length)
+stringFromBuffer(const unsigned char *buffer, size_t length)
 {
 	for (size_t i = 0; i < length; i++)
 		if (buffer[i] == '\0')
 			length = i;
 
-	return [OFString stringWithUTF8String: buffer
+	return [OFString stringWithUTF8String: (const char *)buffer
 				       length: length];
 }
 
 static void
 stringToBuffer(unsigned char *buffer, OFString *string, size_t length)
@@ -49,13 +49,22 @@
 	for (size_t i = UTF8StringLength; i < length; i++)
 		buffer[i] = '\0';
 }
 
 static uintmax_t
-octalValueFromBuffer(const char *buffer, size_t length, uintmax_t max)
+octalValueFromBuffer(const unsigned char *buffer, size_t length, uintmax_t max)
 {
-	uintmax_t value = [stringFromBuffer(buffer, length) octalValue];
+	uintmax_t value;
+
+	if (length == 0)
+		return 0;
+
+	if (buffer[0] == 0x80) {
+		for (size_t i = 1; i < length; i++)
+			value = (value << 8) | buffer[i];
+	} else
+		value = [stringFromBuffer(buffer, length) octalValue];
 
 	if (value > max)
 		@throw [OFOutOfRangeException exception];
 
 	return value;
@@ -70,25 +79,25 @@
 - init
 {
 	OF_INVALID_INIT_METHOD
 }
 
-- (instancetype)of_initWithHeader: (char [512])header
+- (instancetype)of_initWithHeader: (unsigned char [512])header
 {
 	self = [super init];
 
 	@try {
 		void *pool = objc_autoreleasePoolPush();
 		OFString *targetFileName;
 
 		_fileName = [stringFromBuffer(header, 100) copy];
-		_mode = (uint16_t)octalValueFromBuffer(
-		    header + 100, 8, UINT16_MAX);
-		_UID = (uint16_t)octalValueFromBuffer(
-		    header + 108, 8, UINT16_MAX);
-		_GID = (uint16_t)octalValueFromBuffer(
-		    header + 116, 8, UINT16_MAX);
+		_mode = (uint32_t)octalValueFromBuffer(
+		    header + 100, 8, UINT32_MAX);
+		_UID = (uint32_t)octalValueFromBuffer(
+		    header + 108, 8, UINT32_MAX);
+		_GID = (uint32_t)octalValueFromBuffer(
+		    header + 116, 8, UINT32_MAX);
 		_size = (uint64_t)octalValueFromBuffer(
 		    header + 124, 12, UINT64_MAX);
 		_modificationDate = [[OFDate alloc]
 		    initWithTimeIntervalSince1970:
 		    (of_time_interval_t)octalValueFromBuffer(
@@ -190,21 +199,21 @@
 - (OFString *)fileName
 {
 	return _fileName;
 }
 
-- (uint16_t)mode
+- (uint32_t)mode
 {
 	return _mode;
 }
 
-- (uint16_t)UID
+- (uint32_t)UID
 {
 	return _UID;
 }
 
-- (uint16_t)GID
+- (uint32_t)GID
 {
 	return _GID;
 }
 
 - (uint64_t)size