diff --git a/README.md b/README.md
index a90ac14..34486fd 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ refine quality issues inside transactions, and deliver hashed artifacts with
 validation evidence.
 
 > **v1.5 release snapshot:** 154 tools · 6 resources · 5 prompt templates ·
-> 1243 collected tests. Runtime discovery through `system_about` is authoritative.
+> 1245 collected tests. Runtime discovery through `system_about` is authoritative.
 
 ## Install in 10 seconds
 
diff --git a/backends/com_backend.py b/backends/com_backend.py
index cffd363..2298f57 100644
--- a/backends/com_backend.py
+++ b/backends/com_backend.py
@@ -59,6 +59,18 @@ if _WIN32_AVAILABLE:
 else:
     _COM_IMPORTS_OK = False
 
+#: What `_run` may catch as a COM failure. A *tuple*, because where pywin32 is
+#: absent the right value is the empty one: `except ()` catches nothing, which
+#: is exactly correct when no `com_error` type exists to be raised.
+#:
+#: `except pywintypes.com_error` used to be written directly, and Python
+#: evaluates that name on the way out of every failed call — not only COM ones.
+#: On any host without pywin32 (all of Linux, and Windows installed without the
+#: `[com]` extra) it raised `NameError: name 'pywintypes' is not defined` and
+#: buried the real exception. A placeholder Exception subclass would be worse
+#: than the bug: it would silently swallow unrelated errors.
+_COM_ERROR: tuple[type[BaseException], ...] = (pywintypes.com_error,) if _COM_IMPORTS_OK else ()
+
 try:
     from PIL import Image as PILImage
 
@@ -682,7 +694,7 @@ class ComBackend(AutoCADBackend):
                 "(press ESC in AutoCAD). Increase COM_CALL_TIMEOUT if a long "
                 "operation is expected."
             ) from e
-        except pywintypes.com_error as e:
+        except _COM_ERROR as e:
             hr = e.args[0] if e.args else 0
             if hr in (-2147221246, -2147221005, -2147417842):
                 _COM_STATE.pop("app", None)
diff --git a/tests/test_com_timeout.py b/tests/test_com_timeout.py
index 446ecb5..3275de7 100644
--- a/tests/test_com_timeout.py
+++ b/tests/test_com_timeout.py
@@ -117,6 +117,10 @@ async def test_genuine_deadline_still_rebuilds_the_executor(com_backend, monkeyp
     assert await asyncio.wait_for(com_backend._run(lambda: "fresh"), timeout=3) == "fresh"
 
 
+def _raise_value_error():
+    raise ValueError("nope")
+
+
 async def test_ordinary_errors_are_unchanged(com_backend, monkeypatch):
     """Sanity: non-timeout failures never touched the executor and still don't."""
     monkeypatch.setattr(config.settings, "com_call_timeout", 5)
@@ -130,3 +134,36 @@ async def test_ordinary_errors_are_unchanged(com_backend, monkeypatch):
 
     assert com_backend._executor is live
     assert await com_backend._run(lambda x: x * 2, 21) == 42
+
+
+# ── the handler must be inert where pywin32 is absent ───────────────────────
+
+
+async def test_an_ordinary_error_survives_a_host_without_pywin32(com_backend, monkeypatch):
+    """`except pywintypes.com_error` is evaluated on the way out of *every*
+    failed call, not only COM ones.
+
+    `pywintypes` is bound only when `sys.platform == "win32"` and the import
+    succeeded, so on Linux — and on a Windows box that installed without the
+    `[com]` extra — that clause raised `NameError: name 'pywintypes' is not
+    defined` and buried the real exception. Every Linux CI leg failed on
+    exactly this; the timeout tests survived only because they matched an
+    earlier `except`.
+
+    Deleting the module attribute reproduces the absent import faithfully: the
+    clause resolves the name through the module globals either way.
+    """
+    monkeypatch.delattr(cb, "pywintypes", raising=False)
+    monkeypatch.setattr(config.settings, "com_call_timeout", 5)
+
+    with pytest.raises(ValueError, match="nope"):
+        await com_backend._run(_raise_value_error)
+
+
+async def test_the_com_error_clause_is_a_tuple_so_it_can_be_empty():
+    """An empty tuple catches nothing, which is the correct behaviour when no
+    `com_error` type exists to be raised — a placeholder Exception subclass
+    would swallow unrelated errors instead."""
+    assert isinstance(cb._COM_ERROR, tuple)
+    if not cb._COM_IMPORTS_OK:
+        assert cb._COM_ERROR == ()