diff --git a/tests/checks/tmux-set.fish b/tests/checks/tmux-set.fish
index 51e686725..9510840d9 100644
--- a/tests/checks/tmux-set.fish
+++ b/tests/checks/tmux-set.fish
@@ -3,6 +3,7 @@
 
 isolated-tmux-start
 isolated-tmux send-keys 'set -g g_u_var foobar' Enter
+tmux-sleep
 isolated-tmux send-keys 'set -U g_u_var barfoo' Enter
 
 tmux-sleep