diff --git a/.ci_support/environment.yml b/.ci_support/environment.yml
index 0e9e9b05f..4b4f1491c 100644
--- a/.ci_support/environment.yml
+++ b/.ci_support/environment.yml
@@ -14,7 +14,7 @@ dependencies:
 - plotly =7.0.0
 - pymatgen =2026.5.4
 - pyscal3 =3.3.2
-- scikit-learn =1.8.0
+- scikit-learn =1.9.1
 - scipy =1.18.0
 - spglib =2.7.0
 - sqsgenerator =0.5.5
diff --git a/pyproject.toml b/pyproject.toml
index 01b77b438..66c24f351 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,7 +45,7 @@ pyscal = ["pyscal3==3.3.2"]
 nglview = ["nglview==4.0.1"]
 matplotlib = ["matplotlib==3.11.2"]
 plotly = ["plotly==7.0.0"]
-clusters = ["scikit-learn==1.8.0"]
+clusters = ["scikit-learn==1.9.1"]
 symmetry = ["spglib==2.7.0"]
 surface = [
     "spglib==2.7.0",