diff --git a/tox.ini b/tox.ini
index a28fc762..95e4ec4d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,6 +10,8 @@ requires =
 isolated_build = true
 
 [testenv]
+# pytest
+allowlist_externals = pytest
 # Suppress display of matplotlib plots generated during docs build
 setenv =
     MPLBACKEND=agg