diff --git a/.github/scripts/test_kilosort4_ci.py b/.github/scripts/test_kilosort4_ci.py
index 0d245e3783..17a55adf5f 100644
--- a/.github/scripts/test_kilosort4_ci.py
+++ b/.github/scripts/test_kilosort4_ci.py
@@ -112,6 +112,10 @@
     PARAMS_TO_TEST_DICT.update({"cluster_neighbors": 11})
     PARAMETERS_NOT_AFFECTING_RESULTS.append("cluster_neighbors")
 
+if parse(kilosort.__version__) >= parse("4.0.37"):
+    PARAMS_TO_TEST_DICT.update({"max_cluster_subset": 20})
+    PARAMETERS_NOT_AFFECTING_RESULTS.append("max_cluster_subset")
+
 
 PARAMS_TO_TEST = list(PARAMS_TO_TEST_DICT.keys())
 
@@ -254,6 +258,8 @@ def test_initialize_ops_arguments(self):
             "device",
             "save_preprocessed_copy",
         ]
+        if parse(kilosort.__version__) >= parse("4.0.37"):
+            expected_arguments += ["gui_mode"]
 
         self._check_arguments(
             initialize_ops,
diff --git a/src/spikeinterface/sorters/external/kilosort4.py b/src/spikeinterface/sorters/external/kilosort4.py
index 6070961ad4..eb94a34edf 100644
--- a/src/spikeinterface/sorters/external/kilosort4.py
+++ b/src/spikeinterface/sorters/external/kilosort4.py
@@ -438,7 +438,9 @@ def _setup_json_probe_map(cls, recording, sorter_output_folder):
         chanMap = np.arange(n_chan)
         xc = positions[:, 0]
         yc = positions[:, 1]
-        kcoords = groups.astype(float)
+        unique_groups = set(groups)
+        group_map = {group: idx for idx, group in enumerate(unique_groups)}
+        kcoords = np.array([group_map[group] for group in groups], dtype=int)
 
         probe = {
             "chanMap": chanMap,