diff --git a/commit-reach.h b/commit-reach.h
index b49ad71..148b56f 100644
--- a/commit-reach.h
+++ b/commit-reach.h
@@ -87,7 +87,7 @@ int can_all_from_reach_with_flag(struct object_array *from,
 				 unsigned int with_flag,
 				 unsigned int assign_flag,
 				 time_t min_commit_date,
-				 uint32_t min_generation);
+				 timestamp_t min_generation);
 int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 		       int commit_date_cutoff);