diff --git a/test/integration-tests/README.md b/test/integration-tests/README.md
index 229e802632..e5f7c76713 100644
--- a/test/integration-tests/README.md
+++ b/test/integration-tests/README.md
@@ -120,6 +120,15 @@ rerun the test.
 `TEST_NO_KVM=1`: Disable qemu KVM auto-detection (may be necessary when you're
 trying to run the *vanilla* qemu and have both qemu and qemu-kvm installed)
 
+`TEST_MKOSI_ARGS=options`: Extra options (split like a shell command line)
+passed to the `mkosi` invocation that launches the test image, without
+affecting the image build. Only the `--option=value` syntax is accepted. For example,
+`TEST_MKOSI_ARGS="--format=directory --output-dir=build/mkosi.output.dir"`
+boots the test container from a directory format output (which has to be built
+beforehand, into a separate output directory), allowing boot mode tests to run
+in environments that can't dissect disk images, such as unprivileged
+containers, where loop devices and udev are not available.
+
 `TEST_MATCH_SUBTEST=subtest`:  If the test makes use of `run_subtests` use this
 variable to provide a POSIX extended regex to run only subtests matching the
 expression.
diff --git a/test/integration-tests/integration-test-wrapper.py b/test/integration-tests/integration-test-wrapper.py
index 19dcf2bc28..1324b6ccd3 100755
--- a/test/integration-tests/integration-test-wrapper.py
+++ b/test/integration-tests/integration-test-wrapper.py
@@ -670,6 +670,12 @@ def main() -> None:
             '''
         )
 
+    # Extra mkosi options for this invocation only. Each has to use the '--option=value' syntax.
+    test_mkosi_args = shlex.split(os.getenv('TEST_MKOSI_ARGS', ''))
+    for arg in test_mkosi_args:
+        if not re.fullmatch('--[^=]+=.*', arg):
+            sys.exit(f"TEST_MKOSI_ARGS must contain only '--option=value' mkosi options, got: {arg}")
+
     cmd = [
         args.mkosi,
         '--directory', os.fspath(args.mkosi_dir),
@@ -713,6 +719,7 @@ def main() -> None:
         ),
         '--credential', f"journal.storage={'persistent' if sys.stdin.isatty() else args.storage}",
         *(['--runtime-build-sources=no', '--register=no'] if not sys.stdin.isatty() else []),
+        *test_mkosi_args,
         'vm' if vm else 'boot',
         *(
             [