diff --git a/src/cluster.c b/src/cluster.c
index 20f56dc..c79addc 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -60,6 +60,7 @@ static long tree_alloc_node(struct b_tree *p)
 	fseek(table->t_storage, pos, SEEK_SET);
 
 	len /= sizeof *n;
+	table->t_nr_groups++;
 
 	return (long)len;
 }
@@ -165,6 +166,8 @@ void cluster_table_init(struct cluster_table *table, FILE *storage)
 			&table->t_base);
 	node_init(root);
 	tree_put_node(&table->t_base, 0, (b_tree_node *)root);
+	table->t_nr_groups++;
+
 	b_tree_cache_release_node(&table->t_base, (b_tree_node *)root);
 }
 
diff --git a/src/cluster.h b/src/cluster.h
index 25a1e72..0df9a61 100644
--- a/src/cluster.h
+++ b/src/cluster.h
@@ -1,12 +1,13 @@
 #ifndef CLUSTER_H_
 #define CLUSTER_H_
 
-#include <stdio.h>
-
 #include "b-tree.h"
 
+#include <stdio.h>
+
 struct cluster_table {
 	struct b_tree t_base;
+	size_t t_nr_groups;
 	FILE *t_storage;
 };
 
@@ -21,7 +22,12 @@ struct cluster {
 extern void cluster_table_init(struct cluster_table *table, FILE *storage);
 extern void cluster_table_finish(struct cluster_table *table);
 
-extern int cluster_table_get(struct cluster_table *table, unsigned long id, struct cluster *out);
-extern int cluster_table_put(struct cluster_table *table, const struct cluster *in);
+extern int cluster_table_get(
+	struct cluster_table *table,
+	unsigned long id,
+	struct cluster *out);
+extern int cluster_table_put(
+	struct cluster_table *table,
+	const struct cluster *in);
 
-#endif
\ No newline at end of file
+#endif