diff --git a/noptica.py b/noptica.py
index 06a513b..a3fe8fb 100644
--- a/noptica.py
+++ b/noptica.py
@@ -202,8 +202,8 @@ class LinearPhaseFilter:
         return output
 
     def delay(self):
-        assert(self.numptaps % 2 == 1)
-        return (self.numptaps - 1)//2
+        assert(self.numtaps % 2 == 1)
+        return (self.numtaps - 1)//2
 
 
 class Delay: