diff --git a/.github/workflows/test_kilosort4.yml b/.github/workflows/test_kilosort4.yml
index 1966a2bba2..321c801e78 100644
--- a/.github/workflows/test_kilosort4.yml
+++ b/.github/workflows/test_kilosort4.yml
@@ -3,11 +3,11 @@ name: Testing Kilosort4
 on:
   workflow_dispatch:
   schedule:
-    - cron: "0 12 * * 0"  # Weekly on Sunday at noon UTC
+    - cron: "0 12 * * 0" # Weekly on Sunday at noon UTC
   pull_request:
     paths:
-      - '**/kilosort4.py'
-      - '**/test_kilosort4_ci.py'
+      - "**/kilosort4.py"
+      - "**/test_kilosort4_ci.py"
 
 jobs:
   versions:
@@ -76,6 +76,16 @@ jobs:
         if: matrix.ks_version == '4.0.16' || matrix.ks_version == '4.0.17' || matrix.ks_version == '4.0.18'
         run: uv pip install --system setuptools==78.0.2
 
+      - name: Install legacy numpy for KS4 4.1.1 - 4.1.5
+        if: |
+          matrix.ks_version == '4.1.1' ||
+          matrix.ks_version == '4.1.2' ||
+          matrix.ks_version == '4.1.3' ||
+          matrix.ks_version == '4.1.4' ||
+          matrix.ks_version == '4.1.5' ||
+          matrix.ks_version == '4.1.6'
+        run: uv pip install --system "numpy<2.4"
+
       - name: Install Kilosort
         run: |
           uv pip install --system kilosort==${{ matrix.ks_version }}
diff --git a/src/spikeinterface/sorters/external/kilosort4.py b/src/spikeinterface/sorters/external/kilosort4.py
index 3c47f782ab..e54fb34cda 100644
--- a/src/spikeinterface/sorters/external/kilosort4.py
+++ b/src/spikeinterface/sorters/external/kilosort4.py
@@ -147,6 +147,7 @@ def _setup_recording(cls, recording, sorter_output_folder, params, verbose):
     @classmethod
     def _run_from_folder(cls, sorter_output_folder, params, verbose):
         from kilosort import __version__ as ks_version
+        from numpy import __version__ as np_version
         from kilosort.run_kilosort import (
             set_files,
             initialize_ops,
@@ -161,6 +162,13 @@ def _run_from_folder(cls, sorter_output_folder, params, verbose):
         from kilosort.io import load_probe, RecordingExtractorAsArray, BinaryFiltered, save_preprocessing
         from kilosort.parameters import DEFAULT_SETTINGS
 
+        if (version.parse("4.1.1") <= version.parse(ks_version) <= version.parse("4.1.6")) and version.parse(
+            np_version
+        ) >= version.parse("2.4.0"):
+            raise RuntimeError(
+                "Kilosort versions between 4.1.1 and 4.1.6 are not compatible with numpy versions above 2.4. Either upgrade Kilosort to 4.1.7 or above, or downgrade numpy to 2.3 or below."
+            )
+
         if version.parse(ks_version) >= version.parse("4.0.33"):
             HAS_DIAGNOSTIC_PLOTS = True
             import kilosort.plots as kplots