diff --git a/midx-write.c b/midx-write.c
index 55342fcb6d..4a1a16431a 100644
--- a/midx-write.c
+++ b/midx-write.c
@@ -114,6 +114,12 @@ struct write_midx_context {
 	struct odb_source *source;
 };
 
+static uint32_t midx_pack_perm(struct write_midx_context *ctx,
+			       uint32_t orig_pack_int_id)
+{
+	return ctx->pack_perm[orig_pack_int_id];
+}
+
 static int should_include_pack(const struct write_midx_context *ctx,
 			       const char *file_name)
 {
@@ -509,12 +515,12 @@ static int write_midx_object_offsets(struct hashfile *f,
 	for (i = 0; i < ctx->entries_nr; i++) {
 		struct pack_midx_entry *obj = list++;
 
-		if (ctx->pack_perm[obj->pack_int_id] == PACK_EXPIRED)
+		if (midx_pack_perm(ctx, obj->pack_int_id) == PACK_EXPIRED)
 			BUG("object %s is in an expired pack with int-id %d",
 			    oid_to_hex(&obj->oid),
 			    obj->pack_int_id);
 
-		hashwrite_be32(f, ctx->pack_perm[obj->pack_int_id]);
+		hashwrite_be32(f, midx_pack_perm(ctx, obj->pack_int_id));
 
 		if (ctx->large_offsets_needed && obj->offset >> 31)
 			hashwrite_be32(f, MIDX_LARGE_OFFSET_NEEDED | nr_large_offset++);
@@ -615,7 +621,7 @@ static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 	for (i = 0; i < ctx->entries_nr; i++) {
 		struct pack_midx_entry *e = &ctx->entries[i];
 		data[i].nr = i;
-		data[i].pack = ctx->pack_perm[e->pack_int_id];
+		data[i].pack = midx_pack_perm(ctx, e->pack_int_id);
 		if (!e->preferred)
 			data[i].pack |= (1U << 31);
 		data[i].offset = e->offset;
@@ -625,7 +631,7 @@ static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 
 	for (i = 0; i < ctx->entries_nr; i++) {
 		struct pack_midx_entry *e = &ctx->entries[data[i].nr];
-		struct pack_info *pack = &ctx->info[ctx->pack_perm[e->pack_int_id]];
+		struct pack_info *pack = &ctx->info[midx_pack_perm(ctx, e->pack_int_id)];
 		if (pack->bitmap_pos == BITMAP_POS_UNKNOWN)
 			pack->bitmap_pos = i + base_objects;
 		pack->bitmap_nr++;
@@ -686,7 +692,7 @@ static void prepare_midx_packing_data(struct packing_data *pdata,
 		struct object_entry *to = packlist_alloc(pdata, &from->oid);
 
 		oe_set_in_pack(pdata, to,
-			       ctx->info[ctx->pack_perm[from->pack_int_id]].p);
+			       ctx->info[midx_pack_perm(ctx, from->pack_int_id)].p);
 	}
 
 	trace2_region_leave("midx", "prepare_midx_packing_data", ctx->repo);
@@ -1285,7 +1291,7 @@ static int write_midx_internal(struct write_midx_opts *opts)
 						      sizeof(*ctx.info),
 						      idx_or_pack_name_cmp);
 		if (preferred) {
-			uint32_t perm = ctx.pack_perm[preferred->orig_pack_int_id];
+			uint32_t perm = midx_pack_perm(&ctx, preferred->orig_pack_int_id);
 			if (perm == PACK_EXPIRED)
 				warning(_("preferred pack '%s' is expired"),
 					opts->preferred_pack_name);