diff --git a/CHANGES b/CHANGES
index 93d5f4c452..6c87beb8e9 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,8 @@
+5173.	[bug]		Fixed a race in socket code that could occur when
+			accept, send, or recv were called from an event
+			loop but the socket had been closed by another
+			thread. [RT #874]
+
 5172.	[bug]		nsupdate now honors the operating system's preferred
 			ephemeral port range. [GL #905]
 
diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index 4a3365cb47..00ea6a27cf 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -2816,6 +2816,11 @@ internal_accept(isc__socket_t *sock) {
 	INSIST(VALID_SOCKET(sock));
 
 	LOCK(&sock->lock);
+	if (sock->fd < 0) {
+		/* Socket is gone */
+		UNLOCK(&sock->lock);
+		return;
+	}
 	socket_log(sock, NULL, TRACE,
 		   "internal_accept called, locked socket");
 
@@ -3051,6 +3056,11 @@ internal_recv(isc__socket_t *sock) {
 	INSIST(VALID_SOCKET(sock));
 
 	LOCK(&sock->lock);
+	if (sock->fd < 0) {
+		/* Socket is gone */
+		UNLOCK(&sock->lock);
+		return;
+	}
 	dev = ISC_LIST_HEAD(sock->recv_list);
 	if (dev == NULL) {
 		goto finish;
@@ -3105,6 +3115,11 @@ internal_send(isc__socket_t *sock) {
 	INSIST(VALID_SOCKET(sock));
 
 	LOCK(&sock->lock);
+	if (sock->fd < 0) {
+		/* Socket is gone */
+		UNLOCK(&sock->lock);
+		return;
+	}
 	dev = ISC_LIST_HEAD(sock->send_list);
 	if (dev == NULL) {
 		goto finish;