diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index 863176fac..fbf18a5f2 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -914,7 +914,10 @@ ngx_worker_process_init(ngx_cycle_t *cycle, ngx_uint_t priority)
         ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
                       "sched_setaffinity(0x%08Xl)", cpu_affinity);
 
-        if (sched_setaffinity(0, 32, (cpu_set_t *) &cpu_affinity) == -1) {
+        if (sched_setaffinity(0, sizeof(cpu_affinity),
+                              (cpu_set_t *) &cpu_affinity)
+            == -1)
+        {
             ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                           "sched_setaffinity(0x%08Xl) failed", cpu_affinity);
         }