diff --git a/environment.yml b/environment.yml
index 1f502aded..13e05f58f 100644
--- a/environment.yml
+++ b/environment.yml
@@ -19,7 +19,7 @@ dependencies:
   - pip:
     - quartodoc
   - pyarrow
-  - pydantic
+  - pydantic=1
   - pyogrio
   - pytest
   - pytest-cov
diff --git a/python/ribasim/pyproject.toml b/python/ribasim/pyproject.toml
index 38b8f1a8d..94c4e12f8 100644
--- a/python/ribasim/pyproject.toml
+++ b/python/ribasim/pyproject.toml
@@ -24,7 +24,7 @@ dependencies = [
     "pandas",
     "pandera",
     "pyarrow",
-    "pydantic",
+    "pydantic ~= 1.0",
     "pyogrio",
     "shapely >= 2.0",
     "tomli",