Index: src/OFZIPArchive.m
==================================================================
--- src/OFZIPArchive.m
+++ src/OFZIPArchive.m
@@ -609,13 +609,15 @@
 - initWithStream: (OFStream *)stream
 {
 	self = [super init];
 
 	@try {
+		void *pool = objc_autoreleasePoolPush();
+		OFMutableData *extraField = nil;
 		uint16_t fileNameLength, extraFieldLength;
 		of_string_encoding_t encoding;
-		const uint8_t *ZIP64;
+		size_t ZIP64Index;
 		uint16_t ZIP64Size;
 
 		if ([stream readLittleEndianInt32] != 0x04034B50)
 			@throw [OFInvalidFormatException exception];
 
@@ -633,27 +635,39 @@
 		    ? OF_STRING_ENCODING_UTF_8
 		    : OF_STRING_ENCODING_CODEPAGE_437);
 
 		_fileName = [[stream readStringWithLength: fileNameLength
 						 encoding: encoding] copy];
-		_extraField =
-		    [[stream readDataWithCount: extraFieldLength] copy];
+		if (extraFieldLength > 0)
+			extraField = [[[stream readDataWithCount:
+			    extraFieldLength] mutableCopy] autorelease];
 
 		of_zip_archive_entry_extra_field_find(_extraField,
-		    OF_ZIP_ARCHIVE_ENTRY_EXTRA_FIELD_ZIP64, &ZIP64, &ZIP64Size);
+		    OF_ZIP_ARCHIVE_ENTRY_EXTRA_FIELD_ZIP64, &ZIP64Size);
 
-		if (ZIP64 != NULL) {
+		if (ZIP64Index != OF_NOT_FOUND) {
+			const uint8_t *ZIP64 =
+			    [extraField itemAtIndex: ZIP64Index];
+
 			if (_uncompressedSize == 0xFFFFFFFF)
 				_uncompressedSize = of_zip_archive_read_field64(
 				    &ZIP64, &ZIP64Size);
 			if (_compressedSize == 0xFFFFFFFF)
 				_compressedSize = of_zip_archive_read_field64(
 				    &ZIP64, &ZIP64Size);
 
 			if (ZIP64Size > 0)
 				@throw [OFInvalidFormatException exception];
+
+			[extraField removeItemsInRange:
+			    of_range(ZIP64Index - 4, ZIP64Size + 4)];
 		}
+
+		[extraField makeImmutable];
+		_extraField = [extraField copy];
+
+		objc_autoreleasePoolPop(pool);
 	} @catch (id e) {
 		[self release];
 		@throw e;
 	}
 

Index: src/OFZIPArchiveEntry.h
==================================================================
--- src/OFZIPArchiveEntry.h
+++ src/OFZIPArchiveEntry.h
@@ -226,18 +226,18 @@
  *	  specified tag.
  *
  * @param extraField The extra field to search for an extensible data field with
  *		     the specified tag
  * @param tag The tag to look for
- * @param data A pointer to a pointer that should be set to the start of the
- *	       extra field with the specified tag
  * @param size A pointer to an uint16_t that should be set to the size
+ * @return The index at which the extra field content starts in the OFData, or
+ *	   OF_NOT_FOUND
  */
-extern void of_zip_archive_entry_extra_field_find(OFData *extraField,
-    uint16_t tag, const uint8_t *_Nonnull *_Nonnull data, uint16_t *size);
+extern size_t of_zip_archive_entry_extra_field_find(OFData *extraField,
+    uint16_t tag, uint16_t *size);
 #ifdef __cplusplus
 }
 #endif
 
 OF_ASSUME_NONNULL_END
 
 #import "OFMutableZIPArchiveEntry.h"

Index: src/OFZIPArchiveEntry.m
==================================================================
--- src/OFZIPArchiveEntry.m
+++ src/OFZIPArchiveEntry.m
@@ -108,13 +108,13 @@
 		return [OFString stringWithFormat:
 		    @"%u.%u, unknown %02X",
 		    (version % 0xFF) / 10, (version & 0xFF) % 10, version >> 8];
 }
 
-void
+size_t
 of_zip_archive_entry_extra_field_find(OFData *extraField, uint16_t tag,
-    const uint8_t **data, uint16_t *size)
+    uint16_t *size)
 {
 	const uint8_t *bytes = [extraField items];
 	size_t count = [extraField count];
 
 	for (size_t i = 0; i < count;) {
@@ -128,20 +128,19 @@
 
 		if (i + 3 + currentSize >= count)
 			@throw [OFInvalidFormatException exception];
 
 		if (currentTag == tag) {
-			*data = bytes + i + 4;
 			*size = currentSize;
-			return;
+			return i + 4;
 		}
 
 		i += 4 + currentSize;
 	}
 
-	*data = NULL;
 	*size = 0;
+	return OF_NOT_FOUND;
 }
 
 @implementation OFZIPArchiveEntry
 + (instancetype)entryWithFileName: (OFString *)fileName
 {
@@ -178,13 +177,14 @@
 {
 	self = [super init];
 
 	@try {
 		void *pool = objc_autoreleasePoolPush();
+		OFMutableData *extraField = nil;
 		uint16_t fileNameLength, extraFieldLength, fileCommentLength;
 		of_string_encoding_t encoding;
-		const uint8_t *ZIP64 = NULL;
+		size_t ZIP64Index;
 		uint16_t ZIP64Size;
 
 		if ([stream readLittleEndianInt32] != 0x02014B50)
 			@throw [OFInvalidFormatException exception];
 
@@ -210,21 +210,24 @@
 		    : OF_STRING_ENCODING_CODEPAGE_437);
 
 		_fileName = [[stream readStringWithLength: fileNameLength
 						 encoding: encoding] copy];
 		if (extraFieldLength > 0)
-			_extraField =
-			    [[stream readDataWithCount: extraFieldLength] copy];
+			extraField = [[[stream readDataWithCount:
+			    extraFieldLength] mutableCopy] autorelease];
 		if (fileCommentLength > 0)
 			_fileComment = [[stream
 			    readStringWithLength: fileCommentLength
 					encoding: encoding] copy];
 
-		of_zip_archive_entry_extra_field_find(_extraField,
-		    OF_ZIP_ARCHIVE_ENTRY_EXTRA_FIELD_ZIP64, &ZIP64, &ZIP64Size);
+		ZIP64Index = of_zip_archive_entry_extra_field_find(_extraField,
+		    OF_ZIP_ARCHIVE_ENTRY_EXTRA_FIELD_ZIP64, &ZIP64Size);
 
-		if (ZIP64 != NULL) {
+		if (ZIP64Index != OF_NOT_FOUND) {
+			const uint8_t *ZIP64 =
+			    [_extraField itemAtIndex: ZIP64Index];
+
 			if (_uncompressedSize == 0xFFFFFFFF)
 				_uncompressedSize = of_zip_archive_read_field64(
 				    &ZIP64, &ZIP64Size);
 			if (_compressedSize == 0xFFFFFFFF)
 				_compressedSize = of_zip_archive_read_field64(
@@ -237,12 +240,18 @@
 				_startDiskNumber = of_zip_archive_read_field32(
 				    &ZIP64, &ZIP64Size);
 
 			if (ZIP64Size > 0 || _localFileHeaderOffset < 0)
 				@throw [OFInvalidFormatException exception];
+
+			[extraField removeItemsInRange:
+			    of_range(ZIP64Index - 4, ZIP64Size + 4)];
 		}
 
+		[extraField makeImmutable];
+		_extraField = [extraField copy];
+
 		objc_autoreleasePoolPop(pool);
 	} @catch (id e) {
 		[self release];
 		@throw e;
 	}