diff --git a/environment.3.7.yml b/environment.3.7.yml
index 7f01e8c8..85434308 100644
--- a/environment.3.7.yml
+++ b/environment.3.7.yml
@@ -16,4 +16,4 @@ dependencies:
 - scipy=1.1.0
 - statsmodels=0.9.0
 - sympy=1.1.1
-- pytest-xdist
+- pytest-xdist=1.26.1