diff --git a/src/pickley/__init__.py b/src/pickley/__init__.py
index 6f5c15e..896fd11 100644
--- a/src/pickley/__init__.py
+++ b/src/pickley/__init__.py
@@ -1103,7 +1103,10 @@ class VenvSettings:
     """Allows to define in one place how package_manager and python installation are to be resolved"""
 
     def __init__(self, canonical_name, python_spec, package_manager, uv_seed=None):
-        self.python_spec = python_spec or CFG.get_value("python", package_name=canonical_name)
+        if not python_spec:
+            python_spec = CFG.get_value("python", package_name=canonical_name)
+
+        self.python_spec = python_spec
         self.python_installation = CFG.available_pythons.find_python(python_spec)
         if not package_manager:
             package_manager = CFG.get_value("package_manager", package_name=canonical_name)
diff --git a/tests/test_describe.py b/tests/test_describe.py
index 1972bd8..86ab6f2 100644
--- a/tests/test_describe.py
+++ b/tests/test_describe.py
@@ -10,7 +10,7 @@ def test_describe(cli, monkeypatch):
     assert "pickley: version 1.0 (pinned)\n" in cli.logged.stdout
     assert "entry-points: pickley\n" in cli.logged.stdout
 
-    runez.write(".pk/config.json", '{"bake_time": 300}', logger=None)
+    runez.write(".pk/config.json", '{"bake_time": 300, "pinned": {"cowsay": {"python": "3.999"}}}', logger=None)
     cli.run("-vv describe mgit==1.3.0")
     assert cli.succeeded
     assert " -vv describe " in cli.logged.stdout
@@ -18,6 +18,10 @@ def test_describe(cli, monkeypatch):
     assert "mgit: version 1.3.0" in cli.logged.stdout
     assert "Applying bake_time of 5 minutes" in cli.logged.stdout
 
+    cli.run("-vv describe cowsay")
+    assert cli.failed
+    assert "Invalid python: 3.999 [not available]" in cli.logged
+
     runez.delete(".pk/config.json", logger=None)
     if sys.version_info[:2] >= (3, 10):
         cli.run("describe .")