diff --git a/server/site_tests/tast/control.crosbolt-nightly b/server/site_tests/tast/control.crosbolt-nightly
index fa8ed38..2c1b82d 100644
--- a/server/site_tests/tast/control.crosbolt-nightly
+++ b/server/site_tests/tast/control.crosbolt-nightly
@@ -28,7 +28,8 @@
     job.run_test('tast',
                  host=hosts.create_host(machine),
                  test_exprs=['("group:crosbolt" && crosbolt_nightly)'],
-                 ignore_test_failures=True, max_run_sec=10800,
+                 ignore_test_failures=True,
+                 max_run_sec=14400,  # 4 hours.
                  command_args=args)
 
 parallel_simple(run, machines)
diff --git a/server/site_tests/tast/control.crosbolt-perbuild b/server/site_tests/tast/control.crosbolt-perbuild
index b99c982..e1b484b 100644
--- a/server/site_tests/tast/control.crosbolt-perbuild
+++ b/server/site_tests/tast/control.crosbolt-perbuild
@@ -29,7 +29,7 @@
                  host=hosts.create_host(machine),
                  test_exprs=['("group:crosbolt" && crosbolt_perbuild)'],
                  ignore_test_failures=True,
-                 max_run_sec=18000,  # 5 hours.
+                 max_run_sec=21600,  # 6 hours.
                  command_args=args)
 
 parallel_simple(run, machines)