diff --git a/pm/install.py b/pm/install.py
index fbea7b9d7d..a9575adb23 100644
--- a/pm/install.py
+++ b/pm/install.py
@@ -548,14 +548,20 @@ def _still_declared(package, recorded: list[str]) -> list[str]:
     An extra the source removed (``hindsight``) would otherwise ride the ledger
     into every later ``uv sync`` and fail it with "Extra is not defined". Only
     recorded extras are pruned; an explicitly requested unknown extra still fails.
+    Membership uses PEP 685 names (uv matches ``foo_bar`` to ``foo-bar``); the
+    recorded spelling is what reaches uv.
     """
+    import re
     from pm.features import declared_extras
 
+    def normalized(name: str) -> str:
+        return re.sub(r"[-_.]+", "-", name).lower()
+
     root = package.project_root()
     if not (root / "pyproject.toml").is_file():
         return list(recorded)
-    declared = set(declared_extras(root))
-    return [extra for extra in recorded if extra in declared]
+    declared = {normalized(extra) for extra in declared_extras(root)}
+    return [extra for extra in recorded if normalized(extra) in declared]
 
 
 def venv_is_current(*, extras: list[str] | None = None, plugins: Members | Candidates | None = None,
diff --git a/tests/pm/test_source_update_launch.py b/tests/pm/test_source_update_launch.py
index 0bd0a36a02..377032c315 100644
--- a/tests/pm/test_source_update_launch.py
+++ b/tests/pm/test_source_update_launch.py
@@ -347,6 +347,20 @@ def test_source_update_that_removes_a_recorded_extra_still_syncs(source_launch):
     assert pm.venv_is_current(project_root=root)
 
 
+@pytest.mark.platforms("posix")
+def test_recorded_extra_spelled_differently_from_its_declaration_survives(source_launch):
+    """uv matches extras by PEP 685 name; `launch_extra` is the declared `launch-extra`."""
+    root, store_python, _ = source_launch
+    pm.sync_venv(["all", "launch_extra"], explicit=True, project_root=root)
+    assert _fact(root)["extras"] == ["all", "launch_extra"]
+
+    lock = root / "uv.lock"
+    lock.write_bytes(lock.read_bytes() + b"\n# source update changes the committed lock\n")
+    assert venv_sync.prepare_launch(root, []) == store_python
+    assert _fact(root)["extras"] == ["all", "launch_extra"]
+    assert pm.venv_is_current(project_root=root)
+
+
 @pytest.mark.platforms("posix")
 @pytest.mark.parametrize("mode", ["script", "module", "command"])
 def test_real_bootstrap_reexecs_before_app_imports(source_launch, tmp_path, isolated_python, mode):