diff --git a/kerngen/pisa_generators/ntt.py b/kerngen/pisa_generators/ntt.py
index 316de6cc..dd0ab555 100644
--- a/kerngen/pisa_generators/ntt.py
+++ b/kerngen/pisa_generators/ntt.py
@@ -90,21 +90,20 @@ def to_pisa(self) -> list[PIsaOp]:
         # TODO We need to decide whether output symbols need to be defined
         outtmp = Polys("outtmp", self.output.parts, self.output.rns)
 
-        # control the input for the butterfly method.
+        # Essentially a scalar mul since psi 1 part
         if self.context.ntt_stages % 2 == 0:
-            # Essentially a scalar mul since psi 1 part
+            # Even case: butterfly input starts "coeff"
             mul = Mul(self.context, self.output, self.input0, psi)
-            butterfly_input = outtmp
         else:
+            # Odd case: butterfly input stats with "outtmp"
             mul = Mul(self.context, outtmp, self.input0, psi)
-            butterfly_input = self.input0
 
         butterflies = butterflies_ops(
             pisa_op.NTT,
             context=self.context,
             output=self.output,
             outtmp=outtmp,
-            input0=butterfly_input,
+            input0=self.input0,
         )
 
         return mixed_to_pisa_ops(mul, butterflies)