diff --git a/stages/org.osbuild.kernel-cmdline b/stages/org.osbuild.kernel-cmdline
index b0ea4899..df72094f 100755
--- a/stages/org.osbuild.kernel-cmdline
+++ b/stages/org.osbuild.kernel-cmdline
@@ -29,7 +29,8 @@ MAX_SIZE_MAP = {
 def main(tree, options):
     root_fs_uuid = options.get("root_fs_uuid", "")
     additional = options.get("kernel_opts", "")
-    max_cmdline_size = MAX_SIZE_MAP.get(platform.machine().lower(), 4096)
+    max_cmdline_size = options.get("kernel_cmdline_size",
+                                   MAX_SIZE_MAP.get(platform.machine().lower(), 4096))
 
     params = []
 
diff --git a/stages/org.osbuild.kernel-cmdline.meta.json b/stages/org.osbuild.kernel-cmdline.meta.json
index 4ba73d4e..e511078b 100644
--- a/stages/org.osbuild.kernel-cmdline.meta.json
+++ b/stages/org.osbuild.kernel-cmdline.meta.json
@@ -30,6 +30,12 @@
         "description": "Additional kernel boot options",
         "type": "string",
         "default": ""
+      },
+      "kernel_cmdline_size": {
+        "description": "Sets a custom maximum kernel cmdline size",
+        "type": "integer",
+        "minimum": 256,
+        "maximum": 4096
       }
     }
   }
diff --git a/stages/test/test_kernel_cmdline.py b/stages/test/test_kernel_cmdline.py
new file mode 100644
index 00000000..9b0c87fd
--- /dev/null
+++ b/stages/test/test_kernel_cmdline.py
@@ -0,0 +1,63 @@
+#!/usr/bin/python3
+
+from unittest import mock
+
+import pytest  # type: ignore
+
+from osbuild import testutil
+
+STAGE_NAME = "org.osbuild.kernel-cmdline"
+
+
+@pytest.mark.parametrize("options, expected", [
+    ({"kernel_opts": "--custom-opt=some"}, "--custom-opt=some"),
+    ({"root_fs_uuid": "some-uuid"}, "root=UUID=some-uuid"),
+    ({"root_fs_uuid": "other-uuid", "kernel_opts": "--custom-opt=other"},
+     "root=UUID=other-uuid --custom-opt=other"),
+])
+def test_kernel_cmdline(tmp_path, stage_module, options, expected):
+    tree = tmp_path / "tree"
+    tree.mkdir()
+
+    stage_module.main(tree, options)
+    cmdline_file = tree / "etc" / "kernel" / "cmdline"
+    assert cmdline_file.exists()
+    assert cmdline_file.read_text() == expected
+
+
+@pytest.mark.parametrize("options, arch", [
+    ({"kernel_opts": "a" * 2049}, "x86_64"),
+    ({"kernel_opts": "a" * 1025}, "arm"),
+    ({"kernel_opts": "a" * 2049}, "aarch64"),
+    ({"kernel_opts": "a" * 257, "kernel_cmdline_size": 256}, "any"),
+])
+@mock.patch("platform.machine")
+def test_kernel_opts_size_check(mock_machine, tmp_path, stage_module, options, arch):
+    tree = tmp_path / "tree"
+    tree.mkdir()
+    mock_machine.return_value = arch
+
+    with pytest.raises(ValueError) as e:
+        stage_module.main(tree, options)
+    assert str(e.value).startswith("The size of the kernel cmdline options cannot be larger than")
+
+
+@pytest.mark.parametrize("options, expected_error", [
+    ({"kernel_cmdline_size": 256}, ""),
+    ({"kernel_cmdline_size": 4096}, ""),
+    ({"kernel_cmdline_size": "not integer"}, "is not of type 'integer'"),
+    ({"kernel_cmdline_size": 0}, "is less than the minimum of 256"),
+    ({"kernel_cmdline_size": 4097}, "is greater than the maximum of 4096"),
+])
+def test_schema_validation_kernel_cmdline(stage_schema, options, expected_error):
+    test_input = {
+        "type": STAGE_NAME,
+        "options": options
+    }
+    res = stage_schema.validate(test_input)
+
+    if not expected_error:
+        assert res.valid
+    else:
+        assert not res.valid
+        testutil.assert_jsonschema_error_contains(res, expected_error, expected_num_errs=1)