diff --git a/pyproject.toml b/pyproject.toml
index 1fbdb0c19..f4b7add39 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -88,7 +88,7 @@ full = [
 dev = [
     "xarray<2026.8",  # TODO: drop once linopy ships xarray 2026.3+ compat fix
     "tsam_xarray==0.6.7",  # Time series aggregation for clustering (wraps tsam)
-    "tsam==4.0.0",  # Directly imported for ClusterConfig, ExtremeConfig, SegmentConfig
+    "tsam==4.1.1",  # Directly imported for ClusterConfig, ExtremeConfig, SegmentConfig
     "pytest==9.1.1",
     "pytest-xdist==3.8.0",
     "nbformat==5.11.1",