diff --git a/lib/core-net/adopt.c b/lib/core-net/adopt.c
index a9d2d6d39..4b632ba1d 100644
--- a/lib/core-net/adopt.c
+++ b/lib/core-net/adopt.c
@@ -110,8 +110,8 @@ lws_adopt_descriptor_vhost(struct lws_vhost *vh, lws_adoption_type type,
 			   struct lws *parent)
 {
 	struct lws_context *context = vh->context;
-	struct lws *new_wsi;
 	struct lws_context_per_thread *pt;
+	struct lws *new_wsi;
 	int n;
 
 #if defined(LWS_WITH_PEER_LIMITS)
@@ -133,7 +133,7 @@ lws_adopt_descriptor_vhost(struct lws_vhost *vh, lws_adoption_type type,
 #endif
 
 	/*
-	 * Notice that in SMP case, the wsi may being being created on an
+	 * Notice that in SMP case, the wsi may be being created on an
 	 * entirely different pt / tsi for load balancing.  In that case as
 	 * we initialize it, it may become "live" concurrently unexpectedly...
 	 */
@@ -160,6 +160,21 @@ lws_adopt_descriptor_vhost(struct lws_vhost *vh, lws_adoption_type type,
 		parent->child_list = new_wsi;
 	}
 
+	/* enforce that every fd is nonblocking */
+
+	if (type & LWS_ADOPT_SOCKET) {
+		if (lws_plat_set_nonblocking(fd.sockfd)) {
+			lwsl_err("%s: unable to set sockfd nonblocking\n",
+				 __func__);
+			goto bail;
+		}
+	} else
+		if (lws_plat_set_nonblocking(fd.filefd)) {
+			lwsl_err("%s: unable to set filefd nonblocking\n",
+				 __func__);
+			goto bail;
+		}
+
 	new_wsi->desc = fd;
 
 	if (vh_prot_name) {
diff --git a/lib/core-net/private.h b/lib/core-net/private.h
index c67691379..887bbbd8e 100644
--- a/lib/core-net/private.h
+++ b/lib/core-net/private.h
@@ -728,6 +728,9 @@ user_callback_handle_rxflow(lws_callback_function, struct lws *wsi,
 			    enum lws_callback_reasons reason, void *user,
 			    void *in, size_t len);
 
+LWS_EXTERN int
+lws_plat_set_nonblocking(int fd);
+
 LWS_EXTERN int
 lws_plat_set_socket_options(struct lws_vhost *vhost, lws_sockfd_type fd,
 			    int unix_skt);
diff --git a/lib/plat/esp32/esp32-sockets.c b/lib/plat/esp32/esp32-sockets.c
index 060d72508..de7611a31 100644
--- a/lib/plat/esp32/esp32-sockets.c
+++ b/lib/plat/esp32/esp32-sockets.c
@@ -72,6 +72,11 @@ lws_plat_check_connection_error(struct lws *wsi)
 	return 0;
 }
 
+int
+lws_plat_set_nonblocking(int fd)
+{
+	return fcntl(fd, F_SETFL, O_NONBLOCK) < 0;
+}
 
 int
 lws_plat_set_socket_options(struct lws_vhost *vhost, int fd, int unix_skt)
@@ -126,11 +131,7 @@ lws_plat_set_socket_options(struct lws_vhost *vhost, int fd, int unix_skt)
 	if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &optval, optlen) < 0)
 		return 1;
 
-	/* We are nonblocking... */
-	if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
-		return 1;
-
-	return 0;
+	return lws_plat_set_nonblocking(fd);
 }
 
 /* cast a struct sockaddr_in6 * into addr for ipv6 */
diff --git a/lib/plat/optee/lws-plat-optee.c b/lib/plat/optee/lws-plat-optee.c
index 7103adc16..58e83051c 100644
--- a/lib/plat/optee/lws-plat-optee.c
+++ b/lib/plat/optee/lws-plat-optee.c
@@ -101,6 +101,11 @@ void lwsl_emit_optee(int level, const char *line)
         EMSG("%c%s%s%s%c[0m", 27, colours[m], buf, linecp, 27);
 }
 
+int
+lws_plat_set_nonblocking(int fd)
+{
+	return 0;
+}
 
 void
 lws_plat_drop_app_privileges(const struct lws_context_creation_info *info)
diff --git a/lib/plat/unix/unix-sockets.c b/lib/plat/unix/unix-sockets.c
index 693efd28e..2b5528677 100644
--- a/lib/plat/unix/unix-sockets.c
+++ b/lib/plat/unix/unix-sockets.c
@@ -66,6 +66,11 @@ lws_send_pipe_choked(struct lws *wsi)
 	return 0;
 }
 
+int
+lws_plat_set_nonblocking(int fd)
+{
+	return fcntl(fd, F_SETFL, O_NONBLOCK) < 0;
+}
 
 int
 lws_plat_set_socket_options(struct lws_vhost *vhost, int fd, int unix_skt)
@@ -156,11 +161,7 @@ lws_plat_set_socket_options(struct lws_vhost *vhost, int fd, int unix_skt)
 		return 1;
 #endif
 
-	/* We are nonblocking... */
-	if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
-		return 1;
-
-	return 0;
+	return lws_plat_set_nonblocking(fd);
 }
 
 
diff --git a/lib/plat/windows/windows-sockets.c b/lib/plat/windows/windows-sockets.c
index 3772cfb7e..643e579a1 100644
--- a/lib/plat/windows/windows-sockets.c
+++ b/lib/plat/windows/windows-sockets.c
@@ -42,13 +42,20 @@ lws_poll_listen_fd(struct lws_pollfd *fd)
 	return select(((int)fd->fd) + 1, &readfds, NULL, NULL, &tv);
 }
 
+int
+lws_plat_set_nonblocking(int fd)
+{
+	u_long optl = 1;
+
+	return !!ioctlsocket(fd, FIONBIO, &optl);
+}
+
 int
 lws_plat_set_socket_options(struct lws_vhost *vhost, lws_sockfd_type fd,
 			    int unix_skt)
 {
 	int optval = 1;
 	int optlen = sizeof(optval);
-	u_long optl = 1;
 	DWORD dwBytesRet;
 	struct tcp_keepalive alive;
 	int protonbr;
@@ -87,10 +94,7 @@ lws_plat_set_socket_options(struct lws_vhost *vhost, lws_sockfd_type fd,
 
 	setsockopt(fd, protonbr, TCP_NODELAY, (const char *)&optval, optlen);
 
-	/* We are nonblocking... */
-	ioctlsocket(fd, FIONBIO, &optl);
-
-	return 0;
+	return lws_plat_set_nonblocking(fd);
 }