diff --git a/glotaran/optimization/data.py b/glotaran/optimization/data.py
index 8267c9f17..85780644a 100644
--- a/glotaran/optimization/data.py
+++ b/glotaran/optimization/data.py
@@ -468,7 +468,10 @@ def align_groups(
         # as an alternative to the more elegant xarray built-in which is limited to 32 datasets
         # aligned_group_labels = aligned_groups.str.join(dim="dataset").data
         aligned_group_labels = np.asarray(
-            ["".join(sub_arr.values) for _, sub_arr in aligned_groups.groupby("global")]
+            tuple(
+                "".join(sub_arr.to_numpy().flatten())
+                for _, sub_arr in aligned_groups.groupby("global", squeeze=False)
+            )
         )
 
         group_definitions: dict[str, list[str]] = {}
diff --git a/requirements_pinned.txt b/requirements_pinned.txt
index df2b8a49e..3af339917 100644
--- a/requirements_pinned.txt
+++ b/requirements_pinned.txt
@@ -8,7 +8,7 @@ openpyxl==3.1.5
 pandas==2.2.2
 pydantic==2.8.2
 ruamel.yaml==0.18.6
-scipy==1.14.0
+scipy==1.14.1
 sdtfile==2024.5.24
 tabulate==0.9.0
-xarray==2024.6.0
+xarray==2024.7.0