diff --git a/src/event/modules/ngx_rtsig_module.c b/src/event/modules/ngx_rtsig_module.c
index 5d957ec..4ab2388 100644
--- a/src/event/modules/ngx_rtsig_module.c
+++ b/src/event/modules/ngx_rtsig_module.c
@@ -484,7 +484,7 @@
         overflow_current = 0;
         ngx_event_actions.process = ngx_rtsig_process_overflow;
 
-        return NGX_OK;
+        return NGX_ERROR;
 
     } else if (signo != -1) {
         ngx_accept_mutex_unlock();
diff --git a/src/event/ngx_event.c b/src/event/ngx_event.c
index b4211be..208d171 100644
--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -189,7 +189,7 @@
 
     shared = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
 
-    if (shared == NULL) {
+    if (shared == MAP_FAILED) {
         ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
                       "mmap(MAP_ANON|MAP_SHARED) failed");
         return NGX_ERROR;