diff --git a/pyproject.toml b/pyproject.toml
index 2a8c6db04..3325599c4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,7 +35,7 @@ dependencies = [
     "numpy",
     "pandas",
     "pyarrow",
-    "pydantic>=2.5.0",
+    "pydantic >=2.5.0, <2.7.0",
     "PyYAML",
     "xtgeo>=2.16",
 ]