diff --git a/pairing/Cargo.toml b/pairing/Cargo.toml
index 1c59855e7..d46fad7a2 100644
--- a/pairing/Cargo.toml
+++ b/pairing/Cargo.toml
@@ -2,7 +2,7 @@
 name = "pairing"
 
 # Remember to change version string in README.md.
-version = "0.15.0"
+version = "0.15.1"
 authors = [
     "Sean Bowe <ewillbefull@gmail.com>",
     "Jack Grigg <jack@z.cash>",
@@ -18,7 +18,7 @@ edition ="2018"
 
 [dependencies]
 byteorder = "1"
-ff = { version = "0.5.0", path = "../ff", features = ["derive"] }
+ff = { version = "^0.5.2", path = "../ff", features = ["derive"] }
 group = { version = "0.2.0", path = "../group" }
 rand_core = "0.5"
 
diff --git a/pairing/src/bls12_381/ec.rs b/pairing/src/bls12_381/ec.rs
index 6bebc246b..019b19a6b 100644
--- a/pairing/src/bls12_381/ec.rs
+++ b/pairing/src/bls12_381/ec.rs
@@ -200,7 +200,7 @@ macro_rules! curve_impl {
             type Base = $basefield;
             type Affine = $affine;
 
-            fn random<R: RngCore>(rng: &mut R) -> Self {
+            fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
                 loop {
                     let x = $basefield::random(rng);
                     let greatest = rng.next_u32() % 2 != 0;
diff --git a/pairing/src/bls12_381/fq12.rs b/pairing/src/bls12_381/fq12.rs
index 0d6e066ef..17ae39073 100644
--- a/pairing/src/bls12_381/fq12.rs
+++ b/pairing/src/bls12_381/fq12.rs
@@ -40,7 +40,7 @@ impl Fq12 {
 }
 
 impl Field for Fq12 {
-    fn random<R: RngCore>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
         Fq12 {
             c0: Fq6::random(rng),
             c1: Fq6::random(rng),
diff --git a/pairing/src/bls12_381/fq2.rs b/pairing/src/bls12_381/fq2.rs
index c115dd210..4fd391b34 100644
--- a/pairing/src/bls12_381/fq2.rs
+++ b/pairing/src/bls12_381/fq2.rs
@@ -57,7 +57,7 @@ impl Fq2 {
 }
 
 impl Field for Fq2 {
-    fn random<R: RngCore>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
         Fq2 {
             c0: Fq::random(rng),
             c1: Fq::random(rng),
diff --git a/pairing/src/bls12_381/fq6.rs b/pairing/src/bls12_381/fq6.rs
index e2b49c992..92128ca0f 100644
--- a/pairing/src/bls12_381/fq6.rs
+++ b/pairing/src/bls12_381/fq6.rs
@@ -100,7 +100,7 @@ impl Fq6 {
 }
 
 impl Field for Fq6 {
-    fn random<R: RngCore>(rng: &mut R) -> Self {
+    fn random<R: RngCore + ?std::marker::Sized>(rng: &mut R) -> Self {
         Fq6 {
             c0: Fq2::random(rng),
             c1: Fq2::random(rng),