diff --git a/src/os/unix/ngx_thread.h b/src/os/unix/ngx_thread.h
index a85750d..841636a 100644
--- a/src/os/unix/ngx_thread.h
+++ b/src/os/unix/ngx_thread.h
@@ -36,6 +36,12 @@
 } ngx_mutex_t;
 
 
+#define ngx_thread_sigmask(how, set, oset)                         \
+            (sigprocmask(how, set, oset) == -1) ? ngx_errno : 0
+
+#define ngx_thread_sigmask_n  "sigprocmask()"
+
+
 extern char    *ngx_freebsd_kern_usrstack;
 extern size_t   ngx_thread_stack_size;
 
@@ -75,6 +81,9 @@
 #define ngx_gettid()   ((ngx_int_t) pthread_getspecific(0))
 #define ngx_log_tid    ngx_thread_self()
 
+#define ngx_thread_sigmask     pthread_sigmask
+#define ngx_thread_sigmask_n  "pthread_sigmask()"
+
 #endif