diff --git a/script/local.py b/script/local.py
index e142712..d089eef 100644
--- a/script/local.py
+++ b/script/local.py
@@ -42,7 +42,7 @@ def detect_pucks(ip):
 
 def detect_samples(ip):        
     aux = grayscale(ip, in_place=False)
-    invert(aux)|
+    invert(aux)
     subtract_background(aux)
     auto_threshold(aux)
     binary_open(aux)