diff --git a/ctapipe/core/tests/test_traits.py b/ctapipe/core/tests/test_traits.py
index 43a90ffa4f6..205475f9e03 100644
--- a/ctapipe/core/tests/test_traits.py
+++ b/ctapipe/core/tests/test_traits.py
@@ -433,6 +433,33 @@ class SomeComponent(TelescopeComponent):
     assert config["SomeComponent"]["tel_param1"] == [("type", "*", 6.0)]
 
 
+def test_telescope_parameter_from_cli(mock_subarray):
+    """
+    Test we can pass single default for telescope components via cli
+    see #1559
+    """
+
+    from ctapipe.core import Tool, run_tool
+
+    class SomeComponent(TelescopeComponent):
+        path = TelescopeParameter(Path(), default_value=None).tag(config=True)
+        val = TelescopeParameter(Float(), default_value=1.0).tag(config=True)
+
+    class TelescopeTool(Tool):
+        def setup(self):
+            self.comp = SomeComponent(subarray=mock_subarray, parent=self)
+
+    tool = TelescopeTool()
+    run_tool(tool)
+    assert tool.comp.path == [("type", "*", None)]
+    assert tool.comp.val == [("type", "*", 1.0)]
+
+    tool = TelescopeTool()
+    run_tool(tool, ["--SomeComponent.path", "test.h5", "--SomeComponent.val", "2.0"])
+    assert tool.comp.path == [("type", "*", pathlib.Path("test.h5").absolute())]
+    assert tool.comp.val == [("type", "*", 2.0)]
+
+
 def test_datetimes():
     from astropy import time as t
 
diff --git a/ctapipe/core/traits.py b/ctapipe/core/traits.py
index 0aab8fbf848..2f2d5b0f00d 100644
--- a/ctapipe/core/traits.py
+++ b/ctapipe/core/traits.py
@@ -357,20 +357,25 @@ class TelescopeParameter(List):
     """
 
     klass = TelescopePatternList
+    _valid_defaults = (object,)  # allow everything, we validate the default ourselves
 
     def __init__(self, trait, default_value=Undefined, **kwargs):
+
         if not isinstance(trait, TraitType):
             raise TypeError("trait must be a TraitType instance")
 
-        if (
-            not isinstance(default_value, (UserList, list, List))
-            and default_value is not Undefined
-        ):
-            default_value = trait.validate(self, default_value)
-            default_value = [("type", "*", default_value)]
+        self._trait = trait
+        if default_value != Undefined:
+            default_value = self.validate(self, default_value)
 
         super().__init__(default_value=default_value, **kwargs)
-        self._trait = trait
+
+    def from_string(self, s):
+        val = super().from_string(s)
+        # for strings, parsing fails and traitlets returns None
+        if val == [("type", "*", None)] and s != "None":
+            val = [("type", "*", self._trait.from_string(s))]
+        return val
 
     def validate(self, obj, value):
         # Support a single value for all (check and convert into a default value)