diff --git a/format.c b/format.c
index e950df53..f005c1c4 100644
--- a/format.c
+++ b/format.c
@@ -251,10 +251,11 @@ format_expand(struct format_tree *ft, const char *fmt)
 					continue;
 				}
 			}
-			while (len - off < 2) {
+			while (len - off < 3) {
 				buf = xrealloc(buf, 2, len);
 				len *= 2;
 			}
+			buf[off++] = '#';
 			buf[off++] = ch;
 			continue;
 		}
@@ -321,6 +322,8 @@ format_client(struct format_tree *ft, struct client *c)
 	*strchr(tim, '\n') = '\0';
 	format_add(ft, "client_activity_string", "%s", tim);
 
+	format_add(ft, "client_prefix", "%d", !!(c->flags & CLIENT_PREFIX));
+
 	if (c->tty.flags & TTY_UTF8)
 		format_add(ft, "client_utf8", "%d", 1);
 	else
diff --git a/server-client.c b/server-client.c
index 82189a5c..1cae4733 100644
--- a/server-client.c
+++ b/server-client.c
@@ -418,6 +418,7 @@ server_client_handle_key(struct client *c, int key)
 	if (!(c->flags & CLIENT_PREFIX)) {
 		if (isprefix) {
 			c->flags |= CLIENT_PREFIX;
+			server_status_client(c);
 			return;
 		}
 
@@ -432,6 +433,7 @@ server_client_handle_key(struct client *c, int key)
 
 	/* Prefix key already pressed. Reset prefix and lookup key. */
 	c->flags &= ~CLIENT_PREFIX;
+	server_status_client(c);
 	if ((bd = key_bindings_lookup(key | KEYC_PREFIX)) == NULL) {
 		/* If repeating, treat this as a key, else ignore. */
 		if (c->flags & CLIENT_REPEAT) {
@@ -587,8 +589,11 @@ server_client_repeat_timer(unused int fd, unused short events, void *data)
 {
 	struct client	*c = data;
 
-	if (c->flags & CLIENT_REPEAT)
+	if (c->flags & CLIENT_REPEAT) {
+		if (c->flags & CLIENT_PREFIX)
+			server_status_client(c);
 		c->flags &= ~(CLIENT_PREFIX|CLIENT_REPEAT);
+	}
 }
 
 /* Check if client should be exited. */