diff --git a/tests/pexpects/bind.py b/tests/pexpects/bind.py
index 180e5f2e2..59bc6acdd 100644
--- a/tests/pexpects/bind.py
+++ b/tests/pexpects/bind.py
@@ -259,7 +259,7 @@ expect_prompt("git@", unmatched="ctrl-w does not stop at @")
 
 # Ensure that nul can be bound properly (#3189).
 send("bind -k nul 'echo nul seen'\r")
-expect_prompt
+expect_prompt()
 send("\0" * 3)
 send("\r")
 expect_prompt("nul seen\r\nnul seen\r\nnul seen", unmatched="nul not seen")