diff --git a/src/tox.ini b/src/tox.ini
index 97f2568aef8..dc244c115f6 100644
--- a/src/tox.ini
+++ b/src/tox.ini
@@ -388,7 +388,7 @@ consider_namespace_packages = True
 
 [coverage:run]
 source = sage
-concurrency = multiprocessing
+concurrency = multiprocessing,thread
 data_file = .coverage/.coverage
 disable_warnings = no-data-collected