diff --git a/src/coastsat/SDS_preprocess.py b/src/coastsat/SDS_preprocess.py
index 83a99a4..dde28c1 100644
--- a/src/coastsat/SDS_preprocess.py
+++ b/src/coastsat/SDS_preprocess.py
@@ -971,7 +971,7 @@ def is_set(x, n):
     # erroneously identified as clouds by the CFMASK algorithm applied to the images by the USGS.
     if sum(sum(cloud_mask)) > 0 and sum(sum(~cloud_mask)) > 0:
         cloud_mask = morphology.remove_small_objects(
-            cloud_mask, min_size=40, connectivity=1
+            cloud_mask, max_size=39, connectivity=1
         )
     # this is only for if the cloud mask was applied to the shoreline accidentally
     if cloud_mask_issue:
@@ -983,7 +983,7 @@ def is_set(x, n):
                 cloud_mask_temp, elem
             )  # perform image opening
             cloud_mask_temp = morphology.remove_small_objects(
-                cloud_mask_temp, min_size=100, connectivity=1
+                cloud_mask_temp, max_size=99, connectivity=1
             )
             cloud_mask = np.logical_or(cloud_mask, cloud_mask_temp)
 
diff --git a/tests/test_create_cloud_mask_thresholds.py b/tests/test_create_cloud_mask_thresholds.py
new file mode 100644
index 0000000..7a836ba
--- /dev/null
+++ b/tests/test_create_cloud_mask_thresholds.py
@@ -0,0 +1,54 @@
+import sys
+import types
+import warnings
+
+import numpy as np
+
+
+if "osgeo" not in sys.modules:
+    osgeo_stub = types.ModuleType("osgeo")
+    osgeo_stub.gdal = types.SimpleNamespace()
+    osgeo_stub.osr = types.SimpleNamespace()
+    sys.modules["osgeo"] = osgeo_stub
+
+from coastsat import SDS_preprocess
+
+
+def test_create_cloud_mask_keeps_size_40_removes_size_39_without_deprecation_warning():
+    im_QA = np.zeros((30, 30), dtype=np.uint16)
+    im_QA[1:4, 1:14] = 8  # 39 pixels (3x13)
+    im_QA[10:15, 10:18] = 8  # 40 pixels (5x8)
+
+    with warnings.catch_warnings(record=True) as caught_warnings:
+        warnings.simplefilter("always")
+        cloud_mask = SDS_preprocess.create_cloud_mask(
+            im_QA, satname="L8", cloud_mask_issue=False, collection="C02"
+        )
+
+    assert np.sum(cloud_mask) == 40
+    assert cloud_mask[10:15, 10:18].all()
+    assert not cloud_mask[1:4, 1:14].any()
+    assert not any(
+        issubclass(w.category, FutureWarning) for w in caught_warnings
+    ), "create_cloud_mask should not emit FutureWarning from remove_small_objects."
+
+
+def test_create_cloud_mask_issue_keeps_size_100_removes_size_99(monkeypatch):
+    im_QA = np.zeros((50, 50), dtype=np.uint16)
+    im_QA[1:10, 1:12] = 8  # 99 pixels (9x11)
+    im_QA[20:30, 20:30] = 8  # 100 pixels (10x10)
+
+    monkeypatch.setattr(
+        SDS_preprocess.morphology, "binary_opening", lambda image, _: image
+    )
+    monkeypatch.setattr(
+        SDS_preprocess.morphology, "square", lambda width: np.ones((width, width), dtype=bool)
+    )
+
+    cloud_mask = SDS_preprocess.create_cloud_mask(
+        im_QA, satname="L8", cloud_mask_issue=True, collection="C02"
+    )
+
+    assert np.sum(cloud_mask) == 100
+    assert cloud_mask[20:30, 20:30].all()
+    assert not cloud_mask[1:10, 1:12].any()