diff --git a/plugins/carbon/carbon.c b/plugins/carbon/carbon.c
index 017551ac..5ab2e7e8 100644
--- a/plugins/carbon/carbon.c
+++ b/plugins/carbon/carbon.c
@@ -196,7 +196,7 @@ static int carbon_push_stats(int retry_cycle, time_t now) {
 	for (i = 0; i < uwsgi.numproc; i++) {
 		u_carbon.current_busyness_values[i] = uwsgi.workers[i+1].running_time - u_carbon.last_busyness_values[i];
 		u_carbon.last_busyness_values[i] = uwsgi.workers[i+1].running_time;
-		u_carbon.was_busy[i-1] += uwsgi_worker_is_busy(i+1);
+		u_carbon.was_busy[i] += uwsgi_worker_is_busy(i+1);
 	}
 
 	needs_retry = 0;