diff --git a/src/network/connection.c b/src/network/connection.c
index 08f067a17..8e4627d7f 100644
--- a/src/network/connection.c
+++ b/src/network/connection.c
@@ -118,13 +118,19 @@ get_connections_transfering_count(void)
 	return i;
 }
 
+/** Check whether the pointer @a conn still points to a connection
+ * with the given @a id.  If the struct connection has already been
+ * freed, this returns 0.  By comparing connection.id, this function
+ * can usually detect even the case where a different connection has
+ * been created at the same address.  For that to work, the caller
+ * must save the connection.id before the connection can be deleted.  */
 static inline int
-connection_disappeared(struct connection *conn)
+connection_disappeared(struct connection *conn, unsigned int id)
 {
 	struct connection *c;
 
 	foreach (c, connection_queue)
-		if (conn == c && conn->id == c->id)
+		if (conn == c && id == c->id)
 			return 0;
 
 	return 1;
@@ -361,17 +367,19 @@ set_connection_state(struct connection *conn, struct connection_state state)
 
 	conn->state = state;
 	if (is_in_state(conn->state, S_TRANS)) {
+		const unsigned int id = conn->id;
+
 		if (upload_progress && upload_progress->timer == TIMER_ID_UNDEF) {
 			start_update_progress(upload_progress,
 				(void (*)(void *)) upload_stat_timer, conn);
 			upload_stat_timer(conn);
-			if (connection_disappeared(conn))
+			if (connection_disappeared(conn, id))
 				return;
 		}
 		if (progress->timer == TIMER_ID_UNDEF) {
 			start_update_progress(progress, (void (*)(void *)) stat_timer, conn);
 			update_connection_progress(conn);
-			if (connection_disappeared(conn))
+			if (connection_disappeared(conn, id))
 				return;
 		}
 
@@ -450,13 +458,15 @@ static void
 notify_connection_callbacks(struct connection *conn)
 {
 	struct connection_state state = conn->state;
+	unsigned int id = conn->id;
 	struct download *download, *next;
 
 	foreachsafe (download, next, conn->downloads) {
 		download->cached = conn->cached;
 		if (download->callback)
 			download->callback(download, download->data);
-		if (is_in_progress_state(state) && connection_disappeared(conn))
+		if (is_in_progress_state(state)
+		    && connection_disappeared(conn, id))
 			return;
 	}
 }
diff --git a/src/network/socket.c b/src/network/socket.c
index 29487addd..23a042340 100644
--- a/src/network/socket.c
+++ b/src/network/socket.c
@@ -69,6 +69,16 @@ struct connect_info {
 	struct uri *uri;		 /* For updating the blacklist. */
 };
 
+/** For detecting whether a struct socket has been deleted while a
+ * function was using it.  */
+struct socket_weak_ref {
+	LIST_HEAD(struct socket_weak_ref);
+
+	/** done_socket() resets this to NULL.  */
+	struct socket *socket;
+};
+
+static INIT_LIST_OF(struct socket_weak_ref, socket_weak_refs);
 
 /* To enable logging of tranfers, for debugging purposes. */
 #if 0
@@ -143,6 +153,8 @@ init_socket(void *conn, struct socket_operations *ops)
 void
 done_socket(struct socket *socket)
 {
+	struct socket_weak_ref *ref;
+
 	close_socket(socket);
 
 	if (socket->connect_info)
@@ -150,6 +162,11 @@ done_socket(struct socket *socket)
 
 	mem_free_set(&socket->read_buffer, NULL);
 	mem_free_set(&socket->write_buffer, NULL);
+
+	foreach(ref, socket_weak_refs) {
+		if (ref->socket == socket)
+			ref->socket = NULL;
+	}
 }
 
 void
@@ -935,13 +952,26 @@ void
 read_from_socket(struct socket *socket, struct read_buffer *buffer,
 		 struct connection_state state, socket_read_T done)
 {
+	const int is_buffer_new = (buffer != socket->read_buffer);
+	struct socket_weak_ref ref;
 	select_handler_T write_handler;
 
+	ref.socket = socket;
+	add_to_list(socket_weak_refs, &ref);
+
 	buffer->done = done;
 
 	socket->ops->set_timeout(socket, connection_state(0));
 	socket->ops->set_state(socket, state);
 
+	del_from_list(&ref);
+	if (ref.socket == NULL) {
+		/* socket->ops->set_state deleted the socket. */
+		if (is_buffer_new)
+			mem_free(buffer);
+		return;
+	}
+
 	if (socket->read_buffer && buffer != socket->read_buffer)
 		mem_free(socket->read_buffer);
 	socket->read_buffer = buffer;