diff --git a/pkgs/sagemath-objects/tox.ini b/pkgs/sagemath-objects/tox.ini
index d676cb7d8f5..a1244f7aa8c 100644
--- a/pkgs/sagemath-objects/tox.ini
+++ b/pkgs/sagemath-objects/tox.ini
@@ -15,6 +15,10 @@ setenv =
     # Sage scripts such as sage-runtests like to use $HOME/.sage
     HOME={envdir}
 
+passenv =
+    SAGE_NUM_THREADS
+    SAGE_NUM_THREADS_PARALLEL
+
 whitelist_externals =
     bash