diff --git a/tests/conftest.py b/tests/conftest.py
index a31e89c9..3d5091bb 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -165,7 +165,7 @@ def _check_required_test_dependencies() -> None:
   raise pytest.UsageError(msg)
 
 def _smart_watchdog_exit() -> None:
- if not _pytest_finished_event.wait(timeout=300.0):
+ if not _pytest_finished_event.wait(timeout=600.0):
   os._exit(2)
  import time
  time.sleep(5.0)
@@ -177,11 +177,11 @@ def _unconditional_watchdog_exit() -> None:
  """Hard fail-safe: also signal-based, but with a much longer
  timeout than the smart watchdog.
 
- The smart watchdog (above) uses 300s. This sledgehammer waits
+ The smart watchdog (above) uses 600s. This sledgehammer waits
  900s (15 minutes) for the same signal, so a long-running test
  can take up to 15 minutes before we declare it a hang. The
  only case this catches that the smart doesn't: pytest finishes
- but the test session is so long the smart's 300s expires first.
+ but the test session is so long the smart's 600s expires first.
  In that case we still want the runner to move on.
 
  If the signal never fires (true hang), os._exit(2) so the runner