diff --git a/pykilosort/params.py b/pykilosort/params.py
index 4f5b1b8..0502a04 100644
--- a/pykilosort/params.py
+++ b/pykilosort/params.py
@@ -191,7 +191,7 @@ def validate_deterministic_mode(cls, v, values):
     nfilt_factor: int = Field(
         4, description="max number of clusters per good channel (even temporary ones)"
     )
-    ntbuff = Field(
+    ntbuff: int = Field(
         64,
         description="""
     samples of symmetrical buffer for whitening and spike detection