diff --git a/tests/pexpects/job_summary.py b/tests/pexpects/job_summary.py
index ba2e89486..d9e8984d5 100644
--- a/tests/pexpects/job_summary.py
+++ b/tests/pexpects/job_summary.py
@@ -51,5 +51,7 @@ expect_prompt()
 # cmd_line contains the entire pipeline. proc_id and proc_name are set in a pipeline.
 sendline("true | sleep 6")
 sleep(0.100)
-call(["pkill", "-KILL", "sleep", "-P", str(sp.spawn.pid)])
+# Beware: Mac pkill requires that the -P argument come before the process name,
+# else the -P argument is ignored.
+call(["pkill", "-KILL", "-P", str(sp.spawn.pid), "sleep"])
 expect_re("[0-9]+:1:true|sleep 6:SIGKILL:Forced quit:[0-9]+:sleep", timeout=20)
diff --git a/tests/pexpects/signals.py b/tests/pexpects/signals.py
index 35bc9a64c..4fbf8f163 100644
--- a/tests/pexpects/signals.py
+++ b/tests/pexpects/signals.py
@@ -53,13 +53,13 @@ sendline(
 expect_prompt()
 sendline("sleep 5")
 sleep(0.100)
-subprocess.call(["pkill", "-INT", "sleep", "-P", str(sp.spawn.pid)])
+subprocess.call(["pkill", "-INT", "-P", str(sp.spawn.pid), "sleep"])
 expect_str("fish_kill_signal 2")
 expect_prompt()
 
 sendline("sleep 5")
 sleep(0.100)
-subprocess.call(["pkill", "-TERM", "sleep", "-P", str(sp.spawn.pid)])
+subprocess.call(["pkill", "-TERM",  "-P", str(sp.spawn.pid), "sleep"])
 expect_str("fish_kill_signal 15")
 expect_prompt()