diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index f6a8ff2ce..c963c9597 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -498,11 +498,11 @@ ngx_ssl_handshake(ngx_connection_t *c)
 
     if (n == 1) {
 
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
-        if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+        if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
@@ -569,7 +569,7 @@ ngx_ssl_handshake(ngx_connection_t *c)
         c->read->handler = ngx_ssl_handshake_handler;
         c->write->handler = ngx_ssl_handshake_handler;
 
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
@@ -581,7 +581,7 @@ ngx_ssl_handshake(ngx_connection_t *c)
         c->read->handler = ngx_ssl_handshake_handler;
         c->write->handler = ngx_ssl_handshake_handler;
 
-        if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+        if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
@@ -767,7 +767,7 @@ ngx_ssl_handle_recv(ngx_connection_t *c, int n)
             c->ssl->saved_write_handler = NULL;
             c->write->ready = 1;
 
-            if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+            if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
                 return NGX_ERROR;
             }
 
@@ -795,7 +795,7 @@ ngx_ssl_handle_recv(ngx_connection_t *c, int n)
 
         c->write->ready = 0;
 
-        if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+        if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
@@ -1019,7 +1019,7 @@ ngx_ssl_write(ngx_connection_t *c, u_char *data, size_t size)
             c->ssl->saved_read_handler = NULL;
             c->read->ready = 1;
 
-            if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+            if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
                 return NGX_ERROR;
             }
 
@@ -1047,7 +1047,7 @@ ngx_ssl_write(ngx_connection_t *c, u_char *data, size_t size)
 
         c->read->ready = 0;
 
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
@@ -1147,11 +1147,11 @@ ngx_ssl_shutdown(ngx_connection_t *c)
         c->read->handler = ngx_ssl_shutdown_handler;
         c->write->handler = ngx_ssl_shutdown_handler;
 
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
-        if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+        if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
             return NGX_ERROR;
         }
 
diff --git a/src/event/ngx_event_pipe.c b/src/event/ngx_event_pipe.c
index a9cb21ecb..ca18d7cae 100644
--- a/src/event/ngx_event_pipe.c
+++ b/src/event/ngx_event_pipe.c
@@ -56,7 +56,7 @@ ngx_event_pipe(ngx_event_pipe_t *p, ngx_int_t do_write)
 
         flags = (rev->eof || rev->error) ? NGX_CLOSE_EVENT : 0;
 
-        if (ngx_handle_read_event(rev, flags) == NGX_ERROR) {
+        if (ngx_handle_read_event(rev, flags) != NGX_OK) {
             return NGX_ABORT;
         }
 
@@ -70,7 +70,7 @@ ngx_event_pipe(ngx_event_pipe_t *p, ngx_int_t do_write)
 
     if (p->downstream->fd != -1 && p->downstream->data == p->output_ctx) {
         wev = p->downstream->write;
-        if (ngx_handle_write_event(wev, p->send_lowat) == NGX_ERROR) {
+        if (ngx_handle_write_event(wev, p->send_lowat) != NGX_OK) {
             return NGX_ABORT;
         }
 
diff --git a/src/http/modules/perl/ngx_http_perl_module.c b/src/http/modules/perl/ngx_http_perl_module.c
index 262794256..bad2454ee 100644
--- a/src/http/modules/perl/ngx_http_perl_module.c
+++ b/src/http/modules/perl/ngx_http_perl_module.c
@@ -285,7 +285,7 @@ ngx_http_perl_sleep_handler(ngx_http_request_t *r)
         return;
     }
 
-    if (ngx_handle_write_event(wev, 0) == NGX_ERROR) {
+    if (ngx_handle_write_event(wev, 0) != NGX_OK) {
         ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
     }
 }
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 1e39ec36e..1a774e434 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -215,7 +215,7 @@ ngx_http_init_connection(ngx_connection_t *c)
 
     ngx_add_timer(rev, c->listening->post_accept_timeout);
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
 #if (NGX_STAT_STUB)
         ngx_atomic_fetch_add(ngx_stat_reading, -1);
 #endif
@@ -504,7 +504,7 @@ ngx_http_ssl_handshake(ngx_event_t *rev)
             ngx_add_timer(rev, c->listening->post_accept_timeout);
         }
 
-        if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(rev, 0) != NGX_OK) {
             ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
         }
 
@@ -1038,7 +1038,7 @@ ngx_http_read_request_header(ngx_http_request_t *r)
             ngx_add_timer(rev, cscf->client_header_timeout);
         }
 
-        if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(rev, 0) != NGX_OK) {
             ngx_http_close_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
             return NGX_ERROR;
         }
@@ -1971,7 +1971,7 @@ ngx_http_set_write_handler(ngx_http_request_t *r)
         ngx_add_timer(wev, clcf->send_timeout);
     }
 
-    if (ngx_handle_write_event(wev, clcf->send_lowat) == NGX_ERROR) {
+    if (ngx_handle_write_event(wev, clcf->send_lowat) != NGX_OK) {
         ngx_http_close_request(r, 0);
         return NGX_ERROR;
     }
@@ -2012,7 +2012,7 @@ ngx_http_writer(ngx_http_request_t *r)
         if (!wev->ready) {
             ngx_add_timer(wev, clcf->send_timeout);
 
-            if (ngx_handle_write_event(wev, clcf->send_lowat) == NGX_ERROR) {
+            if (ngx_handle_write_event(wev, clcf->send_lowat) != NGX_OK) {
                 ngx_http_close_request(r, 0);
             }
 
@@ -2024,7 +2024,7 @@ ngx_http_writer(ngx_http_request_t *r)
             ngx_log_debug0(NGX_LOG_DEBUG_HTTP, wev->log, 0,
                            "http writer delayed");
 
-            if (ngx_handle_write_event(wev, clcf->send_lowat) == NGX_ERROR) {
+            if (ngx_handle_write_event(wev, clcf->send_lowat) != NGX_OK) {
                 ngx_http_close_request(r, 0);
             }
 
@@ -2048,7 +2048,7 @@ ngx_http_writer(ngx_http_request_t *r)
             ngx_add_timer(wev, clcf->send_timeout);
         }
 
-        if (ngx_handle_write_event(wev, clcf->send_lowat) == NGX_ERROR) {
+        if (ngx_handle_write_event(wev, clcf->send_lowat) != NGX_OK) {
             ngx_http_close_request(r, 0);
         }
 
@@ -2083,9 +2083,7 @@ ngx_http_block_reading(ngx_http_request_t *r)
     if ((ngx_event_flags & NGX_USE_LEVEL_EVENT)
         && r->connection->read->active)
     {
-        if (ngx_del_event(r->connection->read, NGX_READ_EVENT, 0)
-            == NGX_ERROR)
-        {
+        if (ngx_del_event(r->connection->read, NGX_READ_EVENT, 0) != NGX_OK) {
             ngx_http_close_request(r, 0);
         }
     }
@@ -2147,7 +2145,7 @@ ngx_http_test_reading(ngx_http_request_t *r)
 
     if ((ngx_event_flags & NGX_USE_LEVEL_EVENT) && rev->active) {
 
-        if (ngx_del_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
+        if (ngx_del_event(rev, NGX_READ_EVENT, 0) != NGX_OK) {
             ngx_http_close_request(r, 0);
         }
     }
@@ -2241,7 +2239,7 @@ ngx_http_set_keepalive(ngx_http_request_t *r)
 
     ngx_add_timer(rev, clcf->keepalive_timeout);
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         ngx_http_close_connection(c);
         return;
     }
@@ -2328,7 +2326,7 @@ ngx_http_set_keepalive(ngx_http_request_t *r)
     rev->handler = ngx_http_keepalive_handler;
 
     if (wev->active && (ngx_event_flags & NGX_USE_LEVEL_EVENT)) {
-        if (ngx_del_event(wev, NGX_WRITE_EVENT, 0) == NGX_ERROR) {
+        if (ngx_del_event(wev, NGX_WRITE_EVENT, 0) != NGX_OK) {
             ngx_http_close_connection(c);
             return;
         }
@@ -2453,7 +2451,7 @@ ngx_http_keepalive_handler(ngx_event_t *rev)
     c->log_error = NGX_ERROR_INFO;
 
     if (n == NGX_AGAIN) {
-        if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(rev, 0) != NGX_OK) {
             ngx_http_close_connection(c);
         }
 
@@ -2506,7 +2504,7 @@ ngx_http_set_lingering_close(ngx_http_request_t *r)
     r->lingering_time = ngx_time() + (time_t) (clcf->lingering_time / 1000);
     ngx_add_timer(rev, clcf->lingering_timeout);
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         ngx_http_close_request(r, 0);
         return;
     }
@@ -2515,7 +2513,7 @@ ngx_http_set_lingering_close(ngx_http_request_t *r)
     wev->handler = ngx_http_empty_handler;
 
     if (wev->active && (ngx_event_flags & NGX_USE_LEVEL_EVENT)) {
-        if (ngx_del_event(wev, NGX_WRITE_EVENT, 0) == NGX_ERROR) {
+        if (ngx_del_event(wev, NGX_WRITE_EVENT, 0) != NGX_OK) {
             ngx_http_close_request(r, 0);
             return;
         }
@@ -2574,7 +2572,7 @@ ngx_http_lingering_close_handler(ngx_event_t *rev)
 
     } while (rev->ready);
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         ngx_http_close_request(r, 0);
         return;
     }
diff --git a/src/http/ngx_http_request_body.c b/src/http/ngx_http_request_body.c
index 97c57ce3a..96f59dd95 100644
--- a/src/http/ngx_http_request_body.c
+++ b/src/http/ngx_http_request_body.c
@@ -327,7 +327,7 @@ ngx_http_do_read_client_request_body(ngx_http_request_t *r)
             clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
             ngx_add_timer(c->read, clcf->client_body_timeout);
 
-            if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+            if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
                 return NGX_HTTP_INTERNAL_SERVER_ERROR;
             }
 
@@ -462,7 +462,7 @@ ngx_http_discard_request_body(ngx_http_request_t *r)
 
     r->read_event_handler = ngx_http_read_discarded_request_body_handler;
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
     }
 
@@ -519,7 +519,7 @@ ngx_http_read_discarded_request_body_handler(ngx_http_request_t *r)
 
     /* rc == NGX_AGAIN */
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         c->error = 1;
         ngx_http_finalize_request(r, rc);
         return;
diff --git a/src/mail/ngx_mail_auth_http_module.c b/src/mail/ngx_mail_auth_http_module.c
index 5b9f04238..ec1dcdc00 100644
--- a/src/mail/ngx_mail_auth_http_module.c
+++ b/src/mail/ngx_mail_auth_http_module.c
@@ -268,7 +268,7 @@ ngx_mail_auth_http_write_handler(ngx_event_t *wev)
                 ngx_del_timer(wev);
             }
 
-            if (ngx_handle_write_event(wev, 0) == NGX_ERROR) {
+            if (ngx_handle_write_event(wev, 0) != NGX_OK) {
                 ngx_close_connection(c);
                 ngx_destroy_pool(ctx->pool);
                 ngx_mail_session_internal_server_error(s);
@@ -894,7 +894,7 @@ ngx_mail_auth_sleep_handler(ngx_event_t *rev)
             return;
         }
 
-        if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(rev, 0) != NGX_OK) {
             ngx_mail_close_connection(c);
         }
 
@@ -902,7 +902,7 @@ ngx_mail_auth_sleep_handler(ngx_event_t *rev)
     }
 
     if (rev->active) {
-        if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(rev, 0) != NGX_OK) {
             ngx_mail_close_connection(c);
         }
     }
@@ -1102,7 +1102,7 @@ ngx_mail_auth_http_block_read(ngx_event_t *rev)
     ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                    "mail auth http block read");
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         c = rev->data;
         s = c->data;
 
diff --git a/src/mail/ngx_mail_handler.c b/src/mail/ngx_mail_handler.c
index 6915dc94f..e86877f1a 100644
--- a/src/mail/ngx_mail_handler.c
+++ b/src/mail/ngx_mail_handler.c
@@ -513,7 +513,7 @@ ngx_mail_send(ngx_event_t *wev)
     }
 
     if (s->out.len == 0) {
-        if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+        if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
             ngx_mail_close_connection(c);
         }
 
@@ -552,7 +552,7 @@ ngx_mail_send(ngx_event_t *wev)
 
     ngx_add_timer(c->write, cscf->timeout);
 
-    if (ngx_handle_write_event(c->write, 0) == NGX_ERROR) {
+    if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
         ngx_mail_close_connection(c);
         return;
     }
@@ -579,7 +579,7 @@ ngx_mail_read_command(ngx_mail_session_t *s, ngx_connection_t *c)
     }
 
     if (n == NGX_AGAIN) {
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             ngx_mail_session_internal_server_error(s);
             return NGX_ERROR;
         }
diff --git a/src/mail/ngx_mail_imap_handler.c b/src/mail/ngx_mail_imap_handler.c
index f8ca4f689..780c38fbb 100644
--- a/src/mail/ngx_mail_imap_handler.c
+++ b/src/mail/ngx_mail_imap_handler.c
@@ -46,7 +46,7 @@ ngx_mail_imap_init_session(ngx_mail_session_t *s, ngx_connection_t *c)
 
     ngx_add_timer(c->read, cscf->timeout);
 
-    if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
         ngx_mail_close_connection(c);
     }
 
diff --git a/src/mail/ngx_mail_pop3_handler.c b/src/mail/ngx_mail_pop3_handler.c
index 51763613d..c763f04ff 100644
--- a/src/mail/ngx_mail_pop3_handler.c
+++ b/src/mail/ngx_mail_pop3_handler.c
@@ -67,7 +67,7 @@ ngx_mail_pop3_init_session(ngx_mail_session_t *s, ngx_connection_t *c)
 
     ngx_add_timer(c->read, cscf->timeout);
 
-    if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
         ngx_mail_close_connection(c);
     }
 
diff --git a/src/mail/ngx_mail_proxy_module.c b/src/mail/ngx_mail_proxy_module.c
index 8890002d1..bd2bcf9ea 100644
--- a/src/mail/ngx_mail_proxy_module.c
+++ b/src/mail/ngx_mail_proxy_module.c
@@ -201,7 +201,7 @@ ngx_mail_proxy_block_read(ngx_event_t *rev)
 
     ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy block read");
 
-    if (ngx_handle_read_event(rev, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
         c = rev->data;
         s = c->data;
 
@@ -664,7 +664,7 @@ ngx_mail_proxy_dummy_handler(ngx_event_t *wev)
 
     ngx_log_debug0(NGX_LOG_DEBUG_MAIL, wev->log, 0, "mail proxy dummy handler");
 
-    if (ngx_handle_write_event(wev, 0) == NGX_ERROR) {
+    if (ngx_handle_write_event(wev, 0) != NGX_OK) {
         c = wev->data;
         s = c->data;
 
@@ -947,22 +947,22 @@ ngx_mail_proxy_handler(ngx_event_t *ev)
         return;
     }
 
-    if (ngx_handle_write_event(dst->write, 0) == NGX_ERROR) {
+    if (ngx_handle_write_event(dst->write, 0) != NGX_OK) {
         ngx_mail_proxy_close_session(s);
         return;
     }
 
-    if (ngx_handle_read_event(dst->read, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(dst->read, 0) != NGX_OK) {
         ngx_mail_proxy_close_session(s);
         return;
     }
 
-    if (ngx_handle_write_event(src->write, 0) == NGX_ERROR) {
+    if (ngx_handle_write_event(src->write, 0) != NGX_OK) {
         ngx_mail_proxy_close_session(s);
         return;
     }
 
-    if (ngx_handle_read_event(src->read, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(src->read, 0) != NGX_OK) {
         ngx_mail_proxy_close_session(s);
         return;
     }
diff --git a/src/mail/ngx_mail_smtp_handler.c b/src/mail/ngx_mail_smtp_handler.c
index 1a89f1749..46247239c 100644
--- a/src/mail/ngx_mail_smtp_handler.c
+++ b/src/mail/ngx_mail_smtp_handler.c
@@ -228,7 +228,7 @@ ngx_mail_smtp_greeting(ngx_mail_session_t *s, ngx_connection_t *c)
     timeout = sscf->greeting_delay ? sscf->greeting_delay : cscf->timeout;
     ngx_add_timer(c->read, timeout);
 
-    if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+    if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
         ngx_mail_close_connection(c);
     }
 
@@ -270,7 +270,7 @@ ngx_mail_smtp_invalid_pipelining(ngx_event_t *rev)
 
         ngx_add_timer(c->read, cscf->timeout);
 
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             ngx_mail_close_connection(c);
             return;
         }
@@ -819,7 +819,7 @@ ngx_mail_smtp_discard_command(ngx_mail_session_t *s, ngx_connection_t *c,
     }
 
     if (n == NGX_AGAIN) {
-        if (ngx_handle_read_event(c->read, 0) == NGX_ERROR) {
+        if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             ngx_mail_session_internal_server_error(s);
             return NGX_ERROR;
         }