diff --git a/server-fn.c b/server-fn.c
index 4ecbce9e..03c89cf5 100644
--- a/server-fn.c
+++ b/server-fn.c
@@ -281,7 +281,7 @@ server_link_window(struct session *src, struct winlink *srcwl,
 		dstwl = winlink_find_by_index(&dst->windows, dstidx);
 	if (dstwl != NULL) {
 		if (dstwl->window == srcwl->window)
-			return (0);
+			return (-1);
 		if (killflag) {
 			/*
 			 * Can't use session_detach as it will destroy session