diff --git a/requirements.txt b/requirements.txt
index d36b04c..6972205 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -14,4 +14,4 @@ pyproj==3.4.0
 scikit-learn==1.1.3
 scikit-optimize==0.9.0
 fmpy==0.3.12
-openturns==1.20
\ No newline at end of file
+openturns==1.18
\ No newline at end of file