diff --git a/tools/test.py b/tools/test.py
index 249b52f0569..788d68734fe 100755
--- a/tools/test.py
+++ b/tools/test.py
@@ -959,6 +959,12 @@ def GetTimeout(self, mode, section=''):
     timeout = self.timeout * TIMEOUT_SCALEFACTOR[ARCH_GUESS or 'ia32'][mode]
     if section == 'pummel' or section == 'benchmark':
       timeout = timeout * 6
+    # We run all WPT from one subset in the same process using workers.
+    # As the number of the tests grow, it can take longer to run some of the
+    # subsets, but it's still overall faster than running them in different
+    # processes.
+    elif section == 'wpt':
+      timeout = timeout * 12
     return timeout
 
 def RunTestCases(cases_to_run, progress, tasks, flaky_tests_mode, measure_flakiness):