diff --git a/src/tox.ini b/src/tox.ini
index 8e562cced8e..cc02ba13875 100644
--- a/src/tox.ini
+++ b/src/tox.ini
@@ -296,7 +296,7 @@ doctest_optionflags = NORMALIZE_WHITESPACE ELLIPSIS
 
 [coverage:run]
 source = sage
-concurrency = multiprocessing
+concurrency = multiprocessing,threads
 data_file = .coverage/.coverage
 disable_warnings = no-data-collected