diff --git a/alloc.c b/alloc.c
index cf4f8b61e1..e8ab14f4a1 100644
--- a/alloc.c
+++ b/alloc.c
@@ -94,6 +94,7 @@ void *alloc_commit_node(void)
 	c->object.type = OBJ_COMMIT;
 	c->index = alloc_commit_index();
 	c->graph_pos = COMMIT_NOT_FROM_GRAPH;
+	c->generation = GENERATION_NUMBER_INFINITY;
 	return c;
 }
 
diff --git a/commit-graph.c b/commit-graph.c
index 70fa1b25fd..9ad21c3ffb 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -262,6 +262,8 @@ static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uin
 	date_low = get_be32(commit_data + g->hash_len + 12);
 	item->date = (timestamp_t)((date_high << 32) | date_low);
 
+	item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;
+
 	pptr = &item->parents;
 
 	edge_value = get_be32(commit_data + g->hash_len);
diff --git a/commit.h b/commit.h
index 23a3f364ed..aac3b8c56f 100644
--- a/commit.h
+++ b/commit.h
@@ -10,6 +10,9 @@
 #include "pretty.h"
 
 #define COMMIT_NOT_FROM_GRAPH 0xFFFFFFFF
+#define GENERATION_NUMBER_INFINITY 0xFFFFFFFF
+#define GENERATION_NUMBER_MAX 0x3FFFFFFF
+#define GENERATION_NUMBER_ZERO 0
 
 struct commit_list {
 	struct commit *item;
@@ -30,6 +33,7 @@ struct commit {
 	 */
 	struct tree *maybe_tree;
 	uint32_t graph_pos;
+	uint32_t generation;
 };
 
 extern int save_commit_buffer;