diff --git a/src/stripepy/cli/view.py b/src/stripepy/cli/view.py
index 8ce75e5..5a8f68b 100644
--- a/src/stripepy/cli/view.py
+++ b/src/stripepy/cli/view.py
@@ -38,7 +38,7 @@ def _read_stripes(f: ResultFile, chrom: str) -> pd.DataFrame:
         df1 = pd.concat([geo_lt, bio_lt], axis="columns")
         df2 = pd.concat([geo_ut, bio_ut], axis="columns")
 
-        return pd.concat([df1, df2]).set_index("seed").sort_index()
+        return pd.concat([df1, df2]).set_index("seed").sort_index(kind="stable")
     except Exception as e:
         raise RuntimeError(f'failed to read stripes for chromosome "{chrom}": {e}')
 
diff --git a/src/stripepy/plot.py b/src/stripepy/plot.py
index 0cb3382..f94d6ea 100644
--- a/src/stripepy/plot.py
+++ b/src/stripepy/plot.py
@@ -521,10 +521,10 @@ def fetch(v: npt.NDArray[int], left_bound: int, right_bound: int) -> Tuple[npt.N
 
     min_persistence = result.min_persistence
     lt_idx, lt_seeds = fetch(
-        np.sort(TDA(pd_lt, min_persistence=min_persistence)[2]), start // resolution, end // resolution
+        np.sort(TDA(pd_lt, min_persistence=min_persistence)[2], stable=True), start // resolution, end // resolution
     )
     ut_idx, ut_seeds = fetch(
-        np.sort(TDA(pd_ut, min_persistence=min_persistence)[2]), start // resolution, end // resolution
+        np.sort(TDA(pd_ut, min_persistence=min_persistence)[2], stable=True), start // resolution, end // resolution
     )
 
     return {
diff --git a/src/stripepy/utils/TDA.py b/src/stripepy/utils/TDA.py
index 8b198d5..62639fe 100644
--- a/src/stripepy/utils/TDA.py
+++ b/src/stripepy/utils/TDA.py
@@ -27,7 +27,7 @@ def TDA(marginal_pd, min_persistence=0):
     )
 
     # Sorting maximum points (and, as a consequence, the corresponding minimum points) w.r.t. persistence:
-    argsorting = np.argsort(list(zip(*filtered_max_points_and_persistence))[1]).tolist()
+    argsorting = np.argsort(list(zip(*filtered_max_points_and_persistence))[1], stable=True).tolist()
 
     if len(filtered_min_points_and_persistence) == 0:
         filtered_min_points = []
diff --git a/src/stripepy/utils/common.py b/src/stripepy/utils/common.py
index 8fd16f5..8293de8 100644
--- a/src/stripepy/utils/common.py
+++ b/src/stripepy/utils/common.py
@@ -31,7 +31,7 @@ def sort_based_on_arg0(*vectors: Sequence) -> Tuple[NDArray]:
     if len(vectors[0]) == 0:
         return tuple((np.array(v) for v in vectors))  # noqa
 
-    permutation = np.argsort(vectors[0])
+    permutation = np.argsort(vectors[0], stable=True)
 
     return tuple((np.array(v)[permutation] for v in vectors))  # noqa
 
diff --git a/src/stripepy/utils/persistence1d.py b/src/stripepy/utils/persistence1d.py
index 3e38fab..81e0294 100644
--- a/src/stripepy/utils/persistence1d.py
+++ b/src/stripepy/utils/persistence1d.py
@@ -41,7 +41,7 @@ def run_persistence(data, level_sets="lower"):
 
     # Number of data to break ties (leftmost index comes first):
     num_elements = len(data)
-    sorted_idx = np.argsort(data, kind="stable")[::-1] if level_sets == "upper" else np.argsort(data, kind="stable")
+    sorted_idx = np.argsort(data, stable=True)[::-1] if level_sets == "upper" else np.argsort(data, stable=True)
 
     # Get a union find data structure:
     uf = UnionFind(num_elements)