diff --git a/commit-graph.c b/commit-graph.c
index 4377b547c8..ca26870d1b 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -350,6 +350,16 @@ static int graph_read_commit_data(const unsigned char *chunk_start,
 	return 0;
 }
 
+static int graph_read_generation_data(const unsigned char *chunk_start,
+				      size_t chunk_size, void *data)
+{
+	struct commit_graph *g = data;
+	if (chunk_size != g->num_commits * sizeof(uint32_t))
+		return error("commit-graph generations chunk is wrong size");
+	g->chunk_generation_data = chunk_start;
+	return 0;
+}
+
 static int graph_read_bloom_data(const unsigned char *chunk_start,
 				  size_t chunk_size, void *data)
 {
@@ -439,8 +449,8 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
 		   &graph->chunk_base_graphs_size);
 
 	if (s->commit_graph_generation_version >= 2) {
-		pair_chunk_unsafe(cf, GRAPH_CHUNKID_GENERATION_DATA,
-			&graph->chunk_generation_data);
+		read_chunk(cf, GRAPH_CHUNKID_GENERATION_DATA,
+			   graph_read_generation_data, graph);
 		pair_chunk_unsafe(cf, GRAPH_CHUNKID_GENERATION_DATA_OVERFLOW,
 			&graph->chunk_generation_data_overflow);
 
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 05bafcfe5f..6505ff595a 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -887,4 +887,12 @@ test_expect_success 'reader notices out-of-bounds extra edge' '
 	test_cmp expect.err err
 '
 
+test_expect_success 'reader notices too-small generations chunk' '
+	check_corrupt_chunk GDA2 clear 00000000 &&
+	cat >expect.err <<-\EOF &&
+	error: commit-graph generations chunk is wrong size
+	EOF
+	test_cmp expect.err err
+'
+
 test_done