diff --git a/requirements.txt b/requirements.txt
index 7b114fd9f5cb9..b1042b885d800 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -44,3 +44,4 @@ mplhep
 nbconvert>=7.4.0
 pytest
 setuptools
+jsonschema # for RooFit HS3 validation (using HS3TestSuite)