diff --git a/archive-zip.c b/archive-zip.c
index 8fbac2741aad958272f05cb9db02b5915a195ffb..72d55a58ac60019f9f6175d4c86af47348630762 100644
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -90,7 +90,7 @@ static void copy_le32(unsigned char *dest, unsigned int n)
 static void *zlib_deflate(void *data, unsigned long size,
 		int compression_level, unsigned long *compressed_size)
 {
-	z_stream stream;
+	git_zstream stream;
 	unsigned long maxsize;
 	void *buffer;
 	int result;
diff --git a/builtin/apply.c b/builtin/apply.c
index 530d4bb7e76da8e402f78ab7f981a080d25d6e78..f2edc52818e817e83717f992a6bbd66dad4ef24d 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -1634,7 +1634,7 @@ static inline int metadata_changes(struct patch *patch)
 static char *inflate_it(const void *data, unsigned long size,
 			unsigned long inflated_size)
 {
-	z_stream stream;
+	git_zstream stream;
 	void *out;
 	int st;
 
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index dbfb5da52a9f9bf097c6336ab5bdc55eccf9caae..f65cb373bfee4fb1fcb40d79480eb104e71d5cad 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -265,7 +265,7 @@ static void unlink_base_data(struct base_data *c)
 static void *unpack_entry_data(unsigned long offset, unsigned long size)
 {
 	int status;
-	z_stream stream;
+	git_zstream stream;
 	void *buf = xmalloc(size);
 
 	memset(&stream, 0, sizeof(stream));
@@ -355,7 +355,7 @@ static void *get_data_from_pack(struct object_entry *obj)
 	off_t from = obj[0].idx.offset + obj[0].hdr_size;
 	unsigned long len = obj[1].idx.offset - from;
 	unsigned char *data, *inbuf;
-	z_stream stream;
+	git_zstream stream;
 	int status;
 
 	data = xmalloc(obj->size);
@@ -666,7 +666,7 @@ static void parse_pack_objects(unsigned char *sha1)
 
 static int write_compressed(struct sha1file *f, void *in, unsigned int size)
 {
-	z_stream stream;
+	git_zstream stream;
 	int status;
 	unsigned char outbuf[4096];
 
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 8981dd60669b14ed25449b6afde9a1526bb813c0..c6e2d8766b0ec15fcfe9dc0a60ee81db6750b527 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -126,7 +126,7 @@ static void *get_delta(struct object_entry *entry)
 
 static unsigned long do_compress(void **pptr, unsigned long size)
 {
-	z_stream stream;
+	git_zstream stream;
 	void *in, *out;
 	unsigned long maxsize;
 
@@ -160,7 +160,7 @@ static int check_pack_inflate(struct packed_git *p,
 		off_t len,
 		unsigned long expect)
 {
-	z_stream stream;
+	git_zstream stream;
 	unsigned char fakebuf[4096], *in;
 	int st;
 
@@ -187,12 +187,12 @@ static void copy_pack_data(struct sha1file *f,
 		off_t len)
 {
 	unsigned char *in;
-	unsigned int avail;
+	unsigned long avail;
 
 	while (len) {
 		in = use_pack(p, w_curs, offset, &avail);
 		if (avail > len)
-			avail = (unsigned int)len;
+			avail = (unsigned long)len;
 		sha1write(f, in, avail);
 		offset += avail;
 		len -= avail;
@@ -994,7 +994,7 @@ static void check_object(struct object_entry *entry)
 		const unsigned char *base_ref = NULL;
 		struct object_entry *base_entry;
 		unsigned long used, used_0;
-		unsigned int avail;
+		unsigned long avail;
 		off_t ofs;
 		unsigned char *buf, c;
 
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index f63973c9143c4109a3d1e40df9ec66a32498fe00..14e04e6795bd514fb1fec506073d8a9a71668cfa 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -90,7 +90,7 @@ static void use(int bytes)
 
 static void *get_data(unsigned long size)
 {
-	z_stream stream;
+	git_zstream stream;
 	void *buf = xmalloc(size);
 
 	memset(&stream, 0, sizeof(stream));
diff --git a/cache.h b/cache.h
index 85ac5ec17c9cf4a8dfd725e1f871be8ec4fef867..1784bab7d5ade3c8efa70980c906c2c77085ade6 100644
--- a/cache.h
+++ b/cache.h
@@ -16,18 +16,27 @@
 #endif
 
 #include <zlib.h>
-
-void git_inflate_init(z_streamp strm);
-void git_inflate_init_gzip_only(z_streamp strm);
-void git_inflate_end(z_streamp strm);
-int git_inflate(z_streamp strm, int flush);
-
-void git_deflate_init(z_streamp strm, int level);
-void git_deflate_init_gzip(z_streamp strm, int level);
-void git_deflate_end(z_streamp strm);
-int git_deflate_end_gently(z_streamp strm);
-int git_deflate(z_streamp strm, int flush);
-unsigned long git_deflate_bound(z_streamp, unsigned long);
+typedef struct git_zstream {
+	z_stream z;
+	unsigned long avail_in;
+	unsigned long avail_out;
+	unsigned long total_in;
+	unsigned long total_out;
+	unsigned char *next_in;
+	unsigned char *next_out;
+} git_zstream;
+
+void git_inflate_init(git_zstream *);
+void git_inflate_init_gzip_only(git_zstream *);
+void git_inflate_end(git_zstream *);
+int git_inflate(git_zstream *, int flush);
+
+void git_deflate_init(git_zstream *, int level);
+void git_deflate_init_gzip(git_zstream *, int level);
+void git_deflate_end(git_zstream *);
+int git_deflate_end_gently(git_zstream *);
+int git_deflate(git_zstream *, int flush);
+unsigned long git_deflate_bound(git_zstream *, unsigned long);
 
 #if defined(DT_UNKNOWN) && !defined(NO_D_TYPE_IN_DIRENT)
 #define DTYPE(de)	((de)->d_type)
@@ -991,7 +1000,7 @@ extern struct packed_git *find_sha1_pack(const unsigned char *sha1,
 extern void pack_report(void);
 extern int open_pack_index(struct packed_git *);
 extern void close_pack_index(struct packed_git *);
-extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned int *);
+extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned long *);
 extern void close_pack_windows(struct packed_git *);
 extern void unuse_pack(struct pack_window **);
 extern void free_pack_by_name(const char *);
diff --git a/diff.c b/diff.c
index bac9a4bc22f96fd284a89c8c33a183672da3361b..431873d43ff35d69326053567f91745a904af93a 100644
--- a/diff.c
+++ b/diff.c
@@ -1729,7 +1729,7 @@ static unsigned char *deflate_it(char *data,
 {
 	int bound;
 	unsigned char *deflated;
-	z_stream stream;
+	git_zstream stream;
 
 	memset(&stream, 0, sizeof(stream));
 	git_deflate_init(&stream, zlib_compression_level);
diff --git a/fast-import.c b/fast-import.c
index e4116a4ace927f2d6fb323a654130863ed047dff..1d5e3336a51a4bf19c0ab700565826b438c43266 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1017,7 +1017,7 @@ static int store_object(
 	unsigned char sha1[20];
 	unsigned long hdrlen, deltalen;
 	git_SHA_CTX c;
-	z_stream s;
+	git_zstream s;
 
 	hdrlen = sprintf((char *)hdr,"%s %lu", typename(type),
 		(unsigned long)dat->len) + 1;
@@ -1163,7 +1163,7 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
 	off_t offset;
 	git_SHA_CTX c;
 	git_SHA_CTX pack_file_ctx;
-	z_stream s;
+	git_zstream s;
 	int status = Z_OK;
 
 	/* Determine if we should auto-checkpoint. */
diff --git a/http-backend.c b/http-backend.c
index ab5015d9d90cdbc5ac6126090e7b5a1cbf0bd626..59ad7da605f711af6970d6832db32efd62b6ea97 100644
--- a/http-backend.c
+++ b/http-backend.c
@@ -271,7 +271,7 @@ static struct rpc_service *select_service(const char *name)
 
 static void inflate_request(const char *prog_name, int out)
 {
-	z_stream stream;
+	git_zstream stream;
 	unsigned char in_buf[8192];
 	unsigned char out_buf[8192];
 	unsigned long cnt = 0;
diff --git a/http-push.c b/http-push.c
index ecd67cf40a2780db4d73f9a28e2b961e6752cfeb..1e8a83093758a27b0312f8e0a9e570a138f1177b 100644
--- a/http-push.c
+++ b/http-push.c
@@ -352,7 +352,7 @@ static void start_put(struct transfer_request *request)
 	unsigned long len;
 	int hdrlen;
 	ssize_t size;
-	z_stream stream;
+	git_zstream stream;
 
 	unpacked = read_sha1_file(request->obj->sha1, &type, &len);
 	hdrlen = sprintf(hdr, "%s %lu", typename(type), len) + 1;
diff --git a/http.h b/http.h
index e9ed3c2e8272e43208e75459ec29fd8b6548ae4d..a39304a7ab81a228da73d85fadfd6d7c1103715d 100644
--- a/http.h
+++ b/http.h
@@ -172,7 +172,7 @@ struct http_object_request {
 	unsigned char sha1[20];
 	unsigned char real_sha1[20];
 	git_SHA_CTX c;
-	z_stream stream;
+	git_zstream stream;
 	int zret;
 	int rename;
 	struct active_request_slot *slot;
diff --git a/pack-check.c b/pack-check.c
index a1a521648deee8e7e82c4e2cb7fe8fe03605dc06..0c19b6e5a5677bd14989175abddc119381fac4ef 100644
--- a/pack-check.c
+++ b/pack-check.c
@@ -26,7 +26,7 @@ int check_pack_crc(struct packed_git *p, struct pack_window **w_curs,
 	uint32_t data_crc = crc32(0, NULL, 0);
 
 	do {
-		unsigned int avail;
+		unsigned long avail;
 		void *data = use_pack(p, w_curs, offset, &avail);
 		if (avail > len)
 			avail = len;
@@ -61,7 +61,7 @@ static int verify_packfile(struct packed_git *p,
 
 	git_SHA1_Init(&ctx);
 	do {
-		unsigned int remaining;
+		unsigned long remaining;
 		unsigned char *in = use_pack(p, w_curs, offset, &remaining);
 		offset += remaining;
 		if (!pack_sig_ofs)
diff --git a/remote-curl.c b/remote-curl.c
index 13d8ceede345893b76fa2f15597d90304a50cf8e..bc48a36ef55603def36fa61144c68698a1e0fc15 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -471,7 +471,7 @@ static int post_rpc(struct rpc_state *rpc)
 		 * the transfer time.
 		 */
 		size_t size;
-		z_stream stream;
+		git_zstream stream;
 		int ret;
 
 		memset(&stream, 0, sizeof(stream));
diff --git a/sha1_file.c b/sha1_file.c
index 0eefb6194e177fc36a70da1a90e416389edc7708..94d431907cc6f974277ab912411d2a9de2cb98bf 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -833,7 +833,7 @@ static int in_window(struct pack_window *win, off_t offset)
 unsigned char *use_pack(struct packed_git *p,
 		struct pack_window **w_cursor,
 		off_t offset,
-		unsigned int *left)
+		unsigned long *left)
 {
 	struct pack_window *win = *w_cursor;
 
@@ -1244,7 +1244,7 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 	return used;
 }
 
-static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
+static int unpack_sha1_header(git_zstream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
 {
 	unsigned long size, used;
 	static const char valid_loose_object_type[8] = {
@@ -1291,7 +1291,7 @@ static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned lon
 	return 0;
 }
 
-static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
+static void *unpack_sha1_rest(git_zstream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
 {
 	int bytes = strlen(buffer) + 1;
 	unsigned char *buf = xmallocz(size);
@@ -1390,7 +1390,7 @@ static int parse_sha1_header(const char *hdr, unsigned long *sizep)
 static void *unpack_sha1_file(void *map, unsigned long mapsize, enum object_type *type, unsigned long *size, const unsigned char *sha1)
 {
 	int ret;
-	z_stream stream;
+	git_zstream stream;
 	char hdr[8192];
 
 	ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
@@ -1406,7 +1406,7 @@ unsigned long get_size_from_delta(struct packed_git *p,
 {
 	const unsigned char *data;
 	unsigned char delta_head[20], *in;
-	z_stream stream;
+	git_zstream stream;
 	int st;
 
 	memset(&stream, 0, sizeof(stream));
@@ -1528,7 +1528,7 @@ static int unpack_object_header(struct packed_git *p,
 				unsigned long *sizep)
 {
 	unsigned char *base;
-	unsigned int left;
+	unsigned long left;
 	unsigned long used;
 	enum object_type type;
 
@@ -1641,7 +1641,7 @@ static void *unpack_compressed_entry(struct packed_git *p,
 				    unsigned long size)
 {
 	int st;
-	z_stream stream;
+	git_zstream stream;
 	unsigned char *buffer, *in;
 
 	buffer = xmallocz(size);
@@ -2074,7 +2074,7 @@ static int sha1_loose_object_info(const unsigned char *sha1, unsigned long *size
 	int status;
 	unsigned long mapsize, size;
 	void *map;
-	z_stream stream;
+	git_zstream stream;
 	char hdr[32];
 
 	map = map_sha1_file(sha1, &mapsize);
@@ -2425,7 +2425,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 {
 	int fd, ret;
 	unsigned char compressed[4096];
-	z_stream stream;
+	git_zstream stream;
 	git_SHA_CTX c;
 	unsigned char parano_sha1[20];
 	char *filename;
diff --git a/zlib.c b/zlib.c
index 8f19d2fe388b2a75699d873618da05a15dd4e2a0..fe537e3ff69880f2d5c69575c2c2575bac503323 100644
--- a/zlib.c
+++ b/zlib.c
@@ -22,45 +22,90 @@ static const char *zerr_to_string(int status)
 	}
 }
 
-void git_inflate_init(z_streamp strm)
+/*
+ * avail_in and avail_out in zlib are counted in uInt, which typically
+ * limits the size of the buffer we can use to 4GB when interacting
+ * with zlib in a single call to inflate/deflate.
+ */
+#define ZLIB_BUF_MAX ((uInt)-1)
+static inline uInt zlib_buf_cap(unsigned long len)
+{
+	if (ZLIB_BUF_MAX < len)
+		die("working buffer for zlib too large");
+	return len;
+}
+
+static void zlib_pre_call(git_zstream *s)
+{
+	s->z.next_in = s->next_in;
+	s->z.next_out = s->next_out;
+	s->z.total_in = s->total_in;
+	s->z.total_out = s->total_out;
+	s->z.avail_in = zlib_buf_cap(s->avail_in);
+	s->z.avail_out = zlib_buf_cap(s->avail_out);
+}
+
+static void zlib_post_call(git_zstream *s)
+{
+	s->next_in = s->z.next_in;
+	s->next_out = s->z.next_out;
+	s->total_in = s->z.total_in;
+	s->total_out = s->z.total_out;
+	s->avail_in = s->z.avail_in;
+	s->avail_out = s->z.avail_out;
+}
+
+void git_inflate_init(git_zstream *strm)
 {
-	int status = inflateInit(strm);
+	int status;
 
+	zlib_pre_call(strm);
+	status = inflateInit(&strm->z);
+	zlib_post_call(strm);
 	if (status == Z_OK)
 		return;
 	die("inflateInit: %s (%s)", zerr_to_string(status),
-	    strm->msg ? strm->msg : "no message");
+	    strm->z.msg ? strm->z.msg : "no message");
 }
 
-void git_inflate_init_gzip_only(z_streamp strm)
+void git_inflate_init_gzip_only(git_zstream *strm)
 {
 	/*
 	 * Use default 15 bits, +16 is to accept only gzip and to
 	 * yield Z_DATA_ERROR when fed zlib format.
 	 */
 	const int windowBits = 15 + 16;
-	int status = inflateInit2(strm, windowBits);
+	int status;
 
+	zlib_pre_call(strm);
+	status = inflateInit2(&strm->z, windowBits);
+	zlib_post_call(strm);
 	if (status == Z_OK)
 		return;
 	die("inflateInit2: %s (%s)", zerr_to_string(status),
-	    strm->msg ? strm->msg : "no message");
+	    strm->z.msg ? strm->z.msg : "no message");
 }
 
-void git_inflate_end(z_streamp strm)
+void git_inflate_end(git_zstream *strm)
 {
-	int status = inflateEnd(strm);
+	int status;
 
+	zlib_pre_call(strm);
+	status = inflateEnd(&strm->z);
+	zlib_post_call(strm);
 	if (status == Z_OK)
 		return;
 	error("inflateEnd: %s (%s)", zerr_to_string(status),
-	      strm->msg ? strm->msg : "no message");
+	      strm->z.msg ? strm->z.msg : "no message");
 }
 
-int git_inflate(z_streamp strm, int flush)
+int git_inflate(git_zstream *strm, int flush)
 {
-	int status = inflate(strm, flush);
+	int status;
 
+	zlib_pre_call(strm);
+	status = inflate(&strm->z, flush);
+	zlib_post_call(strm);
 	switch (status) {
 	/* Z_BUF_ERROR: normal, needs more space in the output buffer */
 	case Z_BUF_ERROR:
@@ -74,7 +119,7 @@ int git_inflate(z_streamp strm, int flush)
 		break;
 	}
 	error("inflate: %s (%s)", zerr_to_string(status),
-	      strm->msg ? strm->msg : "no message");
+	      strm->z.msg ? strm->z.msg : "no message");
 	return status;
 }
 
@@ -82,56 +127,74 @@ int git_inflate(z_streamp strm, int flush)
 #define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
 #endif
 
-unsigned long git_deflate_bound(z_streamp strm, unsigned long size)
+unsigned long git_deflate_bound(git_zstream *strm, unsigned long size)
 {
-	return deflateBound(strm, size);
+	return deflateBound(&strm->z, size);
 }
 
-void git_deflate_init(z_streamp strm, int level)
+void git_deflate_init(git_zstream *strm, int level)
 {
-	int status = deflateInit(strm, level);
+	int status;
 
+	zlib_pre_call(strm);
+	status = deflateInit(&strm->z, level);
+	zlib_post_call(strm);
 	if (status == Z_OK)
 		return;
 	die("deflateInit: %s (%s)", zerr_to_string(status),
-	    strm->msg ? strm->msg : "no message");
+	    strm->z.msg ? strm->z.msg : "no message");
 }
 
-void git_deflate_init_gzip(z_streamp strm, int level)
+void git_deflate_init_gzip(git_zstream *strm, int level)
 {
 	/*
 	 * Use default 15 bits, +16 is to generate gzip header/trailer
 	 * instead of the zlib wrapper.
 	 */
 	const int windowBits = 15 + 16;
-	int status = deflateInit2(strm, level,
+	int status;
+
+	zlib_pre_call(strm);
+	status = deflateInit2(&strm->z, level,
 				  Z_DEFLATED, windowBits,
 				  8, Z_DEFAULT_STRATEGY);
+	zlib_post_call(strm);
 	if (status == Z_OK)
 		return;
 	die("deflateInit2: %s (%s)", zerr_to_string(status),
-	    strm->msg ? strm->msg : "no message");
+	    strm->z.msg ? strm->z.msg : "no message");
 }
 
-void git_deflate_end(z_streamp strm)
+void git_deflate_end(git_zstream *strm)
 {
-	int status = deflateEnd(strm);
+	int status;
 
+	zlib_pre_call(strm);
+	status = deflateEnd(&strm->z);
+	zlib_post_call(strm);
 	if (status == Z_OK)
 		return;
 	error("deflateEnd: %s (%s)", zerr_to_string(status),
-	      strm->msg ? strm->msg : "no message");
+	      strm->z.msg ? strm->z.msg : "no message");
 }
 
-int git_deflate_end_gently(z_streamp strm)
+int git_deflate_end_gently(git_zstream *strm)
 {
-	return deflateEnd(strm);
+	int status;
+
+	zlib_pre_call(strm);
+	status = deflateEnd(&strm->z);
+	zlib_post_call(strm);
+	return status;
 }
 
-int git_deflate(z_streamp strm, int flush)
+int git_deflate(git_zstream *strm, int flush)
 {
-	int status = deflate(strm, flush);
+	int status;
 
+	zlib_pre_call(strm);
+	status = deflate(&strm->z, flush);
+	zlib_post_call(strm);
 	switch (status) {
 	/* Z_BUF_ERROR: normal, needs more space in the output buffer */
 	case Z_BUF_ERROR:
@@ -145,6 +208,6 @@ int git_deflate(z_streamp strm, int flush)
 		break;
 	}
 	error("deflate: %s (%s)", zerr_to_string(status),
-	      strm->msg ? strm->msg : "no message");
+	      strm->z.msg ? strm->z.msg : "no message");
 	return status;
 }