diff --git a/halo2-base/src/poseidon/hasher/mod.rs b/halo2-base/src/poseidon/hasher/mod.rs
index 73c233c6..60e2fe04 100644
--- a/halo2-base/src/poseidon/hasher/mod.rs
+++ b/halo2-base/src/poseidon/hasher/mod.rs
@@ -76,7 +76,7 @@ impl<F: ScalarField, const T: usize, const RATE: usize> PoseidonHasher<F, T, RAT
         &self,
         ctx: &mut Context<F>,
         range: &impl RangeInstructions<F>,
-        inputs: &Vec<AssignedValue<F>>,
+        inputs: &[AssignedValue<F>],
         len: AssignedValue<F>,
     ) -> AssignedValue<F>
     where
@@ -204,7 +204,7 @@ impl<F: ScalarField, const T: usize, const RATE: usize> PoseidonSponge<F, T, RAT
 fn fix_len_array_squeeze<F: ScalarField, const T: usize, const RATE: usize>(
     ctx: &mut Context<F>,
     gate: &impl GateInstructions<F>,
-    input_elements: &Vec<AssignedValue<F>>,
+    input_elements: &[AssignedValue<F>],
     state: &mut PoseidonState<F, T, RATE>,
     spec: &OptimizedPoseidonSpec<F, T, RATE>,
 ) -> AssignedValue<F> {
diff --git a/halo2-base/src/poseidon/hasher/state.rs b/halo2-base/src/poseidon/hasher/state.rs
index 54960ff3..6f23bf5f 100644
--- a/halo2-base/src/poseidon/hasher/state.rs
+++ b/halo2-base/src/poseidon/hasher/state.rs
@@ -205,7 +205,7 @@ impl<F: ScalarField, const T: usize, const RATE: usize> PoseidonState<F, T, RATE
             }
         }
         // If len == 0, inputs_mask is all 0. Then the extra 1 should be added into s[1].
-        let empty_extra_one = gate.sub(ctx, Constant(F::from(1)), inputs_mask[0]);
+        let empty_extra_one = gate.not(ctx, inputs_mask[0]);
         self.s[1] = gate.add(ctx, self.s[1], empty_extra_one);
     }