diff --git a/commit-graph.c b/commit-graph.c
index 6ed649388d..9927762f18 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -272,6 +272,15 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd,
 	graph->data = graph_map;
 	graph->data_len = graph_size;
 
+	if (graph_size < GRAPH_HEADER_SIZE +
+			 (graph->num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH +
+			 GRAPH_FANOUT_SIZE + the_hash_algo->rawsz) {
+		error(_("commit-graph file is too small to hold %u chunks"),
+		      graph->num_chunks);
+		free(graph);
+		return NULL;
+	}
+
 	last_chunk_id = 0;
 	last_chunk_offset = 8;
 	chunk_lookup = data + 8;
@@ -280,13 +289,6 @@ struct commit_graph *parse_commit_graph(void *graph_map, int fd,
 		uint64_t chunk_offset;
 		int chunk_repeated = 0;
 
-		if (data + graph_size - chunk_lookup <
-		    GRAPH_CHUNKLOOKUP_WIDTH) {
-			error(_("commit-graph chunk lookup table entry missing; file may be incomplete"));
-			free(graph);
-			return NULL;
-		}
-
 		chunk_id = get_be32(chunk_lookup + 0);
 		chunk_offset = get_be64(chunk_lookup + 4);
 
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 79e7fbcd40..1073f9e3cf 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -574,7 +574,8 @@ test_expect_success 'detect invalid checksum hash' '
 
 test_expect_success 'detect incorrect chunk count' '
 	corrupt_graph_and_verify $GRAPH_BYTE_CHUNK_COUNT "\377" \
-		"chunk lookup table entry missing" $GRAPH_CHUNK_LOOKUP_OFFSET
+		"commit-graph file is too small to hold [0-9]* chunks" \
+		$GRAPH_CHUNK_LOOKUP_OFFSET
 '
 
 test_expect_success 'git fsck (checks commit-graph)' '