diff --git a/streaming.c b/streaming.c
index bf277daadd..a2c2d88738 100644
--- a/streaming.c
+++ b/streaming.c
@@ -222,27 +222,34 @@ static int close_istream_loose(struct odb_read_stream *st)
 	return 0;
 }
 
-static int open_istream_loose(struct odb_read_stream *st, struct repository *r,
+static int open_istream_loose(struct odb_read_stream **out,
+			      struct repository *r,
 			      const struct object_id *oid)
 {
 	struct object_info oi = OBJECT_INFO_INIT;
+	struct odb_read_stream *st;
 	struct odb_source *source;
-
-	oi.sizep = &st->size;
-	oi.typep = &st->type;
+	unsigned long mapsize;
+	void *mapped;
 
 	odb_prepare_alternates(r->objects);
 	for (source = r->objects->sources; source; source = source->next) {
-		st->u.loose.mapped = odb_source_loose_map_object(source, oid,
-								 &st->u.loose.mapsize);
-		if (st->u.loose.mapped)
+		mapped = odb_source_loose_map_object(source, oid, &mapsize);
+		if (mapped)
 			break;
 	}
-	if (!st->u.loose.mapped)
+	if (!mapped)
 		return -1;
 
-	switch (unpack_loose_header(&st->z, st->u.loose.mapped,
-				    st->u.loose.mapsize, st->u.loose.hdr,
+	/*
+	 * Note: we must allocate this structure early even though we may still
+	 * fail. This is because we need to initialize the zlib stream, and it
+	 * is not possible to copy the stream around after the fact because it
+	 * has self-referencing pointers.
+	 */
+	CALLOC_ARRAY(st, 1);
+
+	switch (unpack_loose_header(&st->z, mapped, mapsize, st->u.loose.hdr,
 				    sizeof(st->u.loose.hdr))) {
 	case ULHR_OK:
 		break;
@@ -250,19 +257,28 @@ static int open_istream_loose(struct odb_read_stream *st, struct repository *r,
 	case ULHR_TOO_LONG:
 		goto error;
 	}
+
+	oi.sizep = &st->size;
+	oi.typep = &st->type;
+
 	if (parse_loose_header(st->u.loose.hdr, &oi) < 0 || st->type < 0)
 		goto error;
 
+	st->u.loose.mapped = mapped;
+	st->u.loose.mapsize = mapsize;
 	st->u.loose.hdr_used = strlen(st->u.loose.hdr) + 1;
 	st->u.loose.hdr_avail = st->z.total_out;
 	st->z_state = z_used;
 	st->close = close_istream_loose;
 	st->read = read_istream_loose;
 
+	*out = st;
+
 	return 0;
 error:
 	git_inflate_end(&st->z);
 	munmap(st->u.loose.mapped, st->u.loose.mapsize);
+	free(st);
 	return -1;
 }
 
@@ -338,12 +354,16 @@ static int close_istream_pack_non_delta(struct odb_read_stream *st)
 	return 0;
 }
 
-static int open_istream_pack_non_delta(struct odb_read_stream *st,
+static int open_istream_pack_non_delta(struct odb_read_stream **out,
 				       struct repository *r UNUSED,
 				       const struct object_id *oid UNUSED,
 				       struct packed_git *pack,
 				       off_t offset)
 {
+	struct odb_read_stream stream = {
+		.close = close_istream_pack_non_delta,
+		.read = read_istream_pack_non_delta,
+	};
 	struct pack_window *window;
 	enum object_type in_pack_type;
 
@@ -352,7 +372,7 @@ static int open_istream_pack_non_delta(struct odb_read_stream *st,
 	in_pack_type = unpack_object_header(pack,
 					    &window,
 					    &offset,
-					    &st->size);
+					    &stream.size);
 	unuse_pack(&window);
 	switch (in_pack_type) {
 	default:
@@ -363,12 +383,13 @@ static int open_istream_pack_non_delta(struct odb_read_stream *st,
 	case OBJ_TAG:
 		break;
 	}
-	st->type = in_pack_type;
-	st->z_state = z_unused;
-	st->close = close_istream_pack_non_delta;
-	st->read = read_istream_pack_non_delta;
-	st->u.in_pack.pack = pack;
-	st->u.in_pack.pos = offset;
+	stream.type = in_pack_type;
+	stream.z_state = z_unused;
+	stream.u.in_pack.pack = pack;
+	stream.u.in_pack.pos = offset;
+
+	CALLOC_ARRAY(*out, 1);
+	**out = stream;
 
 	return 0;
 }
@@ -400,27 +421,35 @@ static ssize_t read_istream_incore(struct odb_read_stream *st, char *buf, size_t
 	return read_size;
 }
 
-static int open_istream_incore(struct odb_read_stream *st, struct repository *r,
+static int open_istream_incore(struct odb_read_stream **out,
+			       struct repository *r,
 			       const struct object_id *oid)
 {
 	struct object_info oi = OBJECT_INFO_INIT;
+	struct odb_read_stream stream = {
+		.close = close_istream_incore,
+		.read = read_istream_incore,
+	};
+	int ret;
 
-	st->u.incore.read_ptr = 0;
-	st->close = close_istream_incore;
-	st->read = read_istream_incore;
+	oi.typep = &stream.type;
+	oi.sizep = &stream.size;
+	oi.contentp = (void **)&stream.u.incore.buf;
+	ret = odb_read_object_info_extended(r->objects, oid, &oi,
+					    OBJECT_INFO_DIE_IF_CORRUPT);
+	if (ret)
+		return ret;
 
-	oi.typep = &st->type;
-	oi.sizep = &st->size;
-	oi.contentp = (void **)&st->u.incore.buf;
-	return odb_read_object_info_extended(r->objects, oid, &oi,
-					     OBJECT_INFO_DIE_IF_CORRUPT);
+	CALLOC_ARRAY(*out, 1);
+	**out = stream;
+	return 0;
 }
 
 /*****************************************************************************
  * static helpers variables and functions for users of streaming interface
  *****************************************************************************/
 
-static int istream_source(struct odb_read_stream *st,
+static int istream_source(struct odb_read_stream **out,
 			  struct repository *r,
 			  const struct object_id *oid)
 {
@@ -435,13 +464,13 @@ static int istream_source(struct odb_read_stream *st,
 
 	switch (oi.whence) {
 	case OI_LOOSE:
-		if (open_istream_loose(st, r, oid) < 0)
+		if (open_istream_loose(out, r, oid) < 0)
 			break;
 		return 0;
 	case OI_PACKED:
 		if (oi.u.packed.is_delta ||
 		    repo_settings_get_big_file_threshold(the_repository) >= size ||
-		    open_istream_pack_non_delta(st, r, oid, oi.u.packed.pack,
+		    open_istream_pack_non_delta(out, r, oid, oi.u.packed.pack,
 						oi.u.packed.offset) < 0)
 			break;
 		return 0;
@@ -449,7 +478,7 @@ static int istream_source(struct odb_read_stream *st,
 		break;
 	}
 
-	return open_istream_incore(st, r, oid);
+	return open_istream_incore(out, r, oid);
 }
 
 /****************************************************************
@@ -474,14 +503,12 @@ struct odb_read_stream *open_istream(struct repository *r,
 				     unsigned long *size,
 				     struct stream_filter *filter)
 {
-	struct odb_read_stream *st = xmalloc(sizeof(*st));
+	struct odb_read_stream *st;
 	const struct object_id *real = lookup_replace_object(r, oid);
-	int ret = istream_source(st, r, real);
+	int ret = istream_source(&st, r, real);
 
-	if (ret) {
-		free(st);
+	if (ret)
 		return NULL;
-	}
 
 	if (filter) {
 		/* Add "&& !is_null_stream_filter(filter)" for performance */