diff --git a/src/groth16/tests/dummy_engine.rs b/src/groth16/tests/dummy_engine.rs
index e4a4040..4b87d9a 100644
--- a/src/groth16/tests/dummy_engine.rs
+++ b/src/groth16/tests/dummy_engine.rs
@@ -417,10 +417,6 @@ impl CurveProjective for Fr {
         AddAssign::add_assign(self, other);
     }
 
-    fn negate(&mut self) {
-        self.0 = self.neg().0;
-    }
-
     fn mul_assign<S: Into<<Self::Scalar as PrimeField>::Repr>>(&mut self, other: S) {
         let tmp = Fr::from_repr(other.into()).unwrap();
 
@@ -499,10 +495,6 @@ impl CurveAffine for Fr {
         <Fr as Field>::is_zero(self)
     }
 
-    fn negate(&mut self) {
-        self.0 = self.neg().0;
-    }
-
     fn mul<S: Into<<Self::Scalar as PrimeField>::Repr>>(&self, other: S) -> Self::Projective {
         let mut res = *self;
         let tmp = Fr::from_repr(other.into()).unwrap();
diff --git a/src/groth16/verifier.rs b/src/groth16/verifier.rs
index 3d9ff08..8ee8a74 100644
--- a/src/groth16/verifier.rs
+++ b/src/groth16/verifier.rs
@@ -1,17 +1,15 @@
 use ff::PrimeField;
 use group::{CurveAffine, CurveProjective};
 use pairing::{Engine, PairingCurveAffine};
-use std::ops::AddAssign;
+use std::ops::{AddAssign, Neg};
 
 use super::{PreparedVerifyingKey, Proof, VerifyingKey};
 
 use crate::SynthesisError;
 
 pub fn prepare_verifying_key<E: Engine>(vk: &VerifyingKey<E>) -> PreparedVerifyingKey<E> {
-    let mut gamma = vk.gamma_g2;
-    gamma.negate();
-    let mut delta = vk.delta_g2;
-    delta.negate();
+    let gamma = vk.gamma_g2.neg();
+    let delta = vk.delta_g2.neg();
 
     PreparedVerifyingKey {
         alpha_g1_beta_g2: E::pairing(vk.alpha_g1, vk.beta_g2),