diff --git a/src/rate_ctr.c b/src/rate_ctr.c
index 9b2459e..bde090a 100644
--- a/src/rate_ctr.c
+++ b/src/rate_ctr.c
@@ -51,6 +51,7 @@
 		return NULL;
 
 	group->desc = desc;
+	group->idx = idx;
 	/* Generate the Group prefix from the user-specified index */
 	group->name_prefix = talloc_size(group, strlen(desc->group_prefix_fmt) + 20);
 	sprintf(group->name_prefix, desc->group_prefix_fmt, idx);