diff --git a/src/shrpx_listen_handler.cc b/src/shrpx_listen_handler.cc
index 3e876966..6a2dacda 100644
--- a/src/shrpx_listen_handler.cc
+++ b/src/shrpx_listen_handler.cc
@@ -67,14 +67,14 @@ void ListenHandler::create_worker_thread(size_t num)
     WorkerInfo *info = &workers_[num_worker_];
     rv = socketpair(AF_UNIX, SOCK_STREAM, 0, info->sv);
     if(rv == -1) {
-      LLOG(ERROR, this) << "socketpair() failed: " << strerror(errno);
+      LLOG(ERROR, this) << "socketpair() failed: errno=" << errno;
       continue;
     }
     info->sv_ssl_ctx = sv_ssl_ctx_;
     info->cl_ssl_ctx = cl_ssl_ctx_;
     rv = pthread_create(&thread, &attr, start_threaded_worker, info);
     if(rv != 0) {
-      LLOG(ERROR, this) << "pthread_create() failed: " << strerror(rv);
+      LLOG(ERROR, this) << "pthread_create() failed: errno=" << rv;
       for(size_t j = 0; j < 2; ++j) {
         close(info->sv[j]);
       }
diff --git a/src/shrpx_spdy_session.cc b/src/shrpx_spdy_session.cc
index e702c10a..187db71c 100644
--- a/src/shrpx_spdy_session.cc
+++ b/src/shrpx_spdy_session.cc
@@ -186,7 +186,7 @@ int SpdySession::init_notification()
   int sockpair[2];
   rv = socketpair(AF_UNIX, SOCK_STREAM, 0, sockpair);
   if(rv == -1) {
-    SSLOG(FATAL, this) << "socketpair() failed: " << strerror(errno);
+    SSLOG(FATAL, this) << "socketpair() failed: errno=" << errno;
     return -1;
   }
   wrbev_ = bufferevent_socket_new(evbase_, sockpair[0],
@@ -258,8 +258,8 @@ void eventcb(bufferevent *bev, short events, void *ptr)
     int val = 1;
     if(setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
                   reinterpret_cast<char *>(&val), sizeof(val)) == -1) {
-      SSLOG(WARNING, spdy) << "Setting option TCP_NODELAY failed: "
-                           << strerror(errno);
+      SSLOG(WARNING, spdy) << "Setting option TCP_NODELAY failed: errno="
+                           << errno;
     }
   } else if(events & BEV_EVENT_EOF) {
     if(LOG_ENABLED(INFO)) {
diff --git a/src/shrpx_spdy_upstream.cc b/src/shrpx_spdy_upstream.cc
index 51a482e9..89e2f341 100644
--- a/src/shrpx_spdy_upstream.cc
+++ b/src/shrpx_spdy_upstream.cc
@@ -518,8 +518,8 @@ void spdy_downstream_eventcb(bufferevent *bev, short events, void *ptr)
     int val = 1;
     if(setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
                   reinterpret_cast<char *>(&val), sizeof(val)) == -1) {
-      DCLOG(WARNING, dconn) << "Setting option TCP_NODELAY failed: "
-                            << strerror(errno);
+      DCLOG(WARNING, dconn) << "Setting option TCP_NODELAY failed: errno="
+                            << errno;
     }
   } else if(events & BEV_EVENT_EOF) {
     if(LOG_ENABLED(INFO)) {
diff --git a/src/shrpx_ssl.cc b/src/shrpx_ssl.cc
index 08332dab..57ccdb6d 100644
--- a/src/shrpx_ssl.cc
+++ b/src/shrpx_ssl.cc
@@ -261,8 +261,8 @@ ClientHandler* accept_connection(event_base *evbase, SSL_CTX *ssl_ctx,
     rv = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
                     reinterpret_cast<char *>(&val), sizeof(val));
     if(rv == -1) {
-      LOG(WARNING) << "Setting option TCP_NODELAY failed: "
-                   << strerror(errno);
+      LOG(WARNING) << "Setting option TCP_NODELAY failed: errno="
+                   << errno;
     }
     SSL *ssl = 0;
     bufferevent *bev;