diff --git a/pycheribuild/boot_cheribsd/__init__.py b/pycheribuild/boot_cheribsd/__init__.py
index 47df03f7e..ecf45ec60 100755
--- a/pycheribuild/boot_cheribsd/__init__.py
+++ b/pycheribuild/boot_cheribsd/__init__.py
@@ -72,7 +72,10 @@
                                                                 CompilationTargets.CHERIBSD_MORELLO_PURECAP,
                                                                 )}
 
-AUTOBOOT_PROMPT = re.compile(r"(H|, h)it \[Enter] to boot ")
+# boot loader without lua: "Hit [Enter] to boot "
+# menu.lua before Sep 2019: ", hit [Enter] to boot "
+# menu.lua: "[Space] to pause"
+AUTOBOOT_PROMPT = re.compile(r"((H|, h)it \[Enter] to boot |\[Space] to pause)")
 BOOT_LOADER_PROMPT = "OK "
 
 STARTING_INIT = "start_init: trying /sbin/init"
@@ -845,6 +848,7 @@ def boot_and_login(child: CheriBSDSpawnMixin, *, starttime, kernel_init_only=Fal
         loader_boot_prompt_messages = [*boot_messages, BOOT_LOADER_PROMPT]
         loader_boot_messages = [*loader_boot_prompt_messages, AUTOBOOT_PROMPT]
         i = child.expect(loader_boot_messages, timeout=20 * 60, timeout_msg="timeout before loader or kernel")
+        ran_manual_boot = False
         if i >= len(boot_messages):
             # Skip 10s wait from loader(8) if we see the autoboot message
             if i == loader_boot_messages.index(AUTOBOOT_PROMPT):  # Hit Enter
@@ -855,7 +859,7 @@ def boot_and_login(child: CheriBSDSpawnMixin, *, starttime, kernel_init_only=Fal
                     i = child.expect(loader_boot_prompt_messages, timeout=60,
                                      timeout_msg="timeout before loader prompt")
                     if i != loader_boot_prompt_messages.index(BOOT_LOADER_PROMPT):
-                        failure("failed to enter boot loader prompt", exit=True)
+                        failure("failed to enter boot loader prompt after stopping autoboot", exit=True)
                         # Fall through to BOOT_LOADER_PROMPT
                 else:
                     child.sendline("\r")
@@ -863,7 +867,10 @@ def boot_and_login(child: CheriBSDSpawnMixin, *, starttime, kernel_init_only=Fal
                 success("===> loader(8) waiting boot commands")
                 # Just boot the default kernel if no alternate kernel directory is given
                 child.sendline("boot {}".format(boot_alternate_kernel_dir or ""))
+                ran_manual_boot = True
             i = child.expect(boot_messages, timeout=5 * 60, timeout_msg="timeout before kernel")
+        if boot_alternate_kernel_dir and not ran_manual_boot:
+            failure("failed to enter boot loader prompt", exit=True)
         if i == boot_messages.index(TRYING_TO_MOUNT_ROOT):
             success("===> mounting rootfs")
             if bootverbose:
diff --git a/pycheribuild/projects/cross/benchmarks.py b/pycheribuild/projects/cross/benchmarks.py
index 29d771e45..058db9767 100644
--- a/pycheribuild/projects/cross/benchmarks.py
+++ b/pycheribuild/projects/cross/benchmarks.py
@@ -483,8 +483,7 @@ def run_tests(self):
             self.fatal("running x86 tests is not implemented yet")
             return
         # testing, not benchmarking -> run only once
-        test_command = "cd '/build/{dirname}' && ./run_jenkins-bluehive.sh -d0 -r1 -s".format(
-            dirname=self.bundle_dir.name)
+        test_command = f"cd '/build/{self.bundle_dir.name}' && ./run_jenkins-bluehive.sh -d0 -r1 -s"
         self.target_info.run_cheribsd_test_script("run_simple_tests.py", "--test-command", test_command,
                                                   "--test-timeout", str(120 * 60), mount_builddir=True)
 
diff --git a/pycheribuild/projects/cross/libcxx.py b/pycheribuild/projects/cross/libcxx.py
index b579a0999..79de531c7 100644
--- a/pycheribuild/projects/cross/libcxx.py
+++ b/pycheribuild/projects/cross/libcxx.py
@@ -330,16 +330,13 @@ def add_cross_flags(self):
         elif self.nfs_mounted_path:
             self.libcxx_lit_jobs = " -j1"  # We can only run one job here since we are using scp
             self.fatal("nfs_mounted_path not portend to new libc++ test infrastructure yet")
-            executor = "SSHExecutorWithNFSMount(\\\"{host}\\\", nfs_dir=\\\"{nfs_dir}\\\"," \
-                       "path_in_target=\\\"{nfs_in_target}\\\", config=self, username=\\\"{user}\\\"," \
-                       " port={port})".format(host=self.qemu_host, user=self.qemu_user, port=self.qemu_port,
-                                              nfs_dir=self.nfs_mounted_path, nfs_in_target=self.nfs_path_in_qemu)
+            executor = f"SSHExecutorWithNFSMount(\\\"{self.qemu_host}\\\", nfs_dir=\\\"{self.nfs_mounted_path}\\\"," \
+                       f"path_in_target=\\\"{self.nfs_path_in_qemu}\\\", config=self," \
+                       f"username=\\\"{self.qemu_user}\\\", port={self.qemu_port})"
         else:
             self.libcxx_lit_jobs = " -j1"  # We can only run one job here since we are using scp
             executor = self.commandline_to_str([self.source_dir / "utils/ssh.py",
-                                                "--host", "{user}@{host}:{port}".format(host=self.qemu_host,
-                                                                                        user=self.qemu_user,
-                                                                                        port=self.qemu_port)])
+                                                "--host", f"{self.qemu_user}@{self.qemu_host}:{self.qemu_port}"])
         if self.target_info.is_baremetal():
             target_info = "libcxx.test.target_info.BaremetalNewlibTI"
         else:
diff --git a/pycheribuild/projects/repository.py b/pycheribuild/projects/repository.py
index a73487b71..f0851c12a 100644
--- a/pycheribuild/projects/repository.py
+++ b/pycheribuild/projects/repository.py
@@ -263,8 +263,7 @@ def ensure_cloned(self, current_project: "Project", *, src_dir: Path, base_proje
         default_clone_branch = self.get_default_branch(current_project, include_per_target=False)
         assert target_override is not None, "Default src != base src -> must have a per-target override"
         assert target_override.branch != default_clone_branch, \
-            "Cannot create worktree with same branch as base repo: {} vs {}".format(target_override.branch,
-                                                                                    default_clone_branch)
+            f"Cannot create worktree with same branch as base repo: {target_override.branch} vs {default_clone_branch}"
         if (src_dir / ".git").exists():
             return
         current_project.info("Creating git-worktree checkout of", base_project_source_dir, "with branch",
diff --git a/test-scripts/run_libcxx_tests.py b/test-scripts/run_libcxx_tests.py
index 087b74bcb..382590170 100755
--- a/test-scripts/run_libcxx_tests.py
+++ b/test-scripts/run_libcxx_tests.py
@@ -314,8 +314,7 @@ def run_parallel_impl(args: argparse.Namespace, processes: "list[LitShardProcess
                     if len(not_booted_processes) == 0:
                         boot_cheribsd.success("All shards have booted succesfully. Releasing barrier (num_waiting = ",
                                               mp_barrier.n_waiting, ")")
-                        assert mp_barrier.n_waiting == len(processes), "{} != {}".format(mp_barrier.n_waiting,
-                                                                                         len(processes))
+                        assert mp_barrier.n_waiting == len(processes), f"{mp_barrier.n_waiting} != {len(processes)}"
                         mp_barrier.wait(timeout=10)
                         boot_cheribsd.success("Barrier has been released, tests should run now.")
                 # assert target_process.stage < shard_result[2], "STAGE WENT BACKWARDS?"