diff --git a/midx.c b/midx.c
index 83857cbd1e..346e58dec7 100644
--- a/midx.c
+++ b/midx.c
@@ -369,6 +369,8 @@ off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos)
 	const unsigned char *offset_data;
 	uint32_t offset32;
 
+	pos = midx_for_object(&m, pos);
+
 	offset_data = m->chunk_object_offsets + (off_t)pos * MIDX_CHUNK_OFFSET_WIDTH;
 	offset32 = get_be32(offset_data + sizeof(uint32_t));