diff --git a/pycheribuild/projects/cross/cheribsd.py b/pycheribuild/projects/cross/cheribsd.py
index 54efb3c9e..18cf69e54 100644
--- a/pycheribuild/projects/cross/cheribsd.py
+++ b/pycheribuild/projects/cross/cheribsd.py
@@ -1099,25 +1099,35 @@ def kernel_make_args_for_config(self, kernconfs: "list[str]", extra_make_args) -
         return kernel_options
 
     def clean(self) -> ThreadJoiner:
-        cleaning_kerneldir = False
-        builddir = self.build_dir
+        cleaning_kerneldirs = False
+        builddirs = None
         if self.config.skip_world:
-            kernel_dir = self.kernel_objdir(self.kernel_config)
-            print(kernel_dir)
-            if kernel_dir and kernel_dir.parent.exists():
-                builddir = kernel_dir
-                cleaning_kerneldir = True
-                if kernel_dir.exists() and self.build_dir.exists():
-                    assert not os.path.relpath(str(kernel_dir.resolve()), str(self.build_dir.resolve())).startswith(
-                        ".."
-                    ), builddir
-            else:
-                self.warning("Do not know the full path to the kernel build directory, will clean the whole tree!")
+            kernel_dirs = [self.kernel_objdir(k) for k in self.kernconf_list()]
+            for kernel_dir in kernel_dirs:
+                print(kernel_dir)
+                if kernel_dir and kernel_dir.parent.exists():
+                    if builddirs is None:
+                        builddirs = []
+                    builddirs.append(kernel_dir)
+                    cleaning_kerneldirs = True
+                    if kernel_dir.exists() and self.build_dir.exists():
+                        assert not os.path.relpath(str(kernel_dir.resolve()), str(self.build_dir.resolve())).startswith(
+                            ".."
+                        ), kernel_dir
+            if builddirs is None:
+                self.warning("Do not know the full path to any kernel build directories, will clean the whole tree!")
+        if builddirs is None:
+            builddirs = [self.build_dir]
+        clean_kwargs = {}
         if self.crossbuild:
             # avoid rebuilding bmake when crossbuilding:
-            return self.async_clean_directory(builddir, keep_root=not cleaning_kerneldir, keep_dirs=["bmake-install"])
-        else:
-            return self.async_clean_directory(builddir)
+            # XXX: Should keep_root be conditional on crossbuild?
+            clean_kwargs["keep_root"] = not cleaning_kerneldirs
+            clean_kwargs["keep_dirs"] = ["bmake-install"]
+        joiner = ThreadJoiner()
+        for builddir in builddirs:
+            joiner += self.async_clean_directory(builddir, **clean_kwargs)
+        return joiner
 
     def _list_kernel_configs(self) -> None:
         """Emit a list of valid kernel configurations that can be given as --kernel-config overrides"""
diff --git a/pycheribuild/utils.py b/pycheribuild/utils.py
index 2f3108188..5a57f99d7 100644
--- a/pycheribuild/utils.py
+++ b/pycheribuild/utils.py
@@ -564,18 +564,31 @@ def uses_zypper(cls) -> bool:
 
 
 class ThreadJoiner:
-    def __init__(self, thread: "Optional[threading.Thread]"):
-        self.thread = thread
+    def __init__(self, threads: "Optional[Union[threading.Thread, list[threading.Thread]]]" = None):
+        if not isinstance(threads, list):
+            if threads is None:
+                self.threads = []
+            else:
+                self.threads = [threads]
+        else:
+            self.threads = threads
 
     def __enter__(self) -> None:
-        if self.thread is not None:
-            self.thread.start()
+        for thread in self.threads:
+            thread.start()
 
     def __exit__(self, *args) -> None:
-        if self.thread is not None:
-            if self.thread.is_alive():
-                status_update("Waiting for '", self.thread.name, "' to complete", sep="")
-            self.thread.join()
+        for thread in self.threads:
+            if thread.is_alive():
+                status_update("Waiting for '", thread.name, "' to complete", sep="")
+            thread.join()
+
+    def __add__(self, other: "ThreadJoiner") -> "ThreadJoiner":
+        return ThreadJoiner(self.threads + other.threads)
+
+    def __iadd__(self, other: "ThreadJoiner") -> "ThreadJoiner":
+        self.threads += other.threads
+        return self
 
 
 def replace_one(s: str, old, new) -> str: