diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index e2d8ae4a02..1008d7f63c 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -430,7 +430,7 @@ static int is_delta_type(enum object_type type)
 	return (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA);
 }
 
-static void *unpack_entry_data(unsigned long offset, unsigned long size,
+static void *unpack_entry_data(off_t offset, unsigned long size,
 			       enum object_type type, unsigned char *sha1)
 {
 	static char fixed_buf[8192];