diff --git a/curve25519-dalek/Cargo.toml b/curve25519-dalek/Cargo.toml
index e08e392..30868cf 100644
--- a/curve25519-dalek/Cargo.toml
+++ b/curve25519-dalek/Cargo.toml
@@ -58,7 +58,7 @@ zeroize = { version = "1", default-features = false, optional = true }
 # Betrusted/Precursor dependency set, enabled by backend_u32e feature
 [target.'cfg(curve25519_dalek_backend = "u32e_backend")'.dependencies]
 log = { version = "0.4"}
-engine25519-as = {git = "https://github.com/betrusted-io/engine25519-as.git", rev = "d249c967556b02ab5439eacb5078fa00c60b93d6", default-features = false, features = []}
+engine25519-as = {git = "https://github.com/betrusted-io/engine25519-as.git", rev = "775e8406eb4aad08f05ae10619fcb4ca891ba0a6", default-features = false, features = []}
 utralib = {version = "0.1.24", default-features = false}
 zeroize = { version = "1", default-features = false }
 xous = "0.9.58"
diff --git a/curve25519-dalek/build.rs b/curve25519-dalek/build.rs
index a04f76b..97fa285 100644
--- a/curve25519-dalek/build.rs
+++ b/curve25519-dalek/build.rs
@@ -2,9 +2,6 @@
 
 #![deny(clippy::unwrap_used, dead_code)]
 
-use platforms::Platform;
-use platforms::target;
-
 #[allow(non_camel_case_types)]
 #[derive(PartialEq, Debug)]
 enum DalekBits {
@@ -12,23 +9,29 @@ enum DalekBits {
     Dalek64,
 }
 
-//TODO: remove debugging before merging
-macro_rules! build_debug {
-    ($($tokens: tt)*) => {
-        println!("cargo:warning={}", format!($($tokens)*))
+use std::fmt::Formatter;
+
+impl std::fmt::Display for DalekBits {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> {
+        let w_bits = match self {
+            DalekBits::Dalek32 => "32",
+            DalekBits::Dalek64 => "64",
+        };
+        write!(f, "{}", w_bits)
     }
 }
 
 fn main() {
-    let target_triplet = std::env::var("TARGET").unwrap();
-    let platform = platforms::Platform::find(&target_triplet).unwrap();
+    let target_arch = match std::env::var("CARGO_CFG_TARGET_ARCH") {
+        Ok(arch) => arch,
+        _ => "".to_string(),
+    };
+
     let curve25519_dalek_bits = match std::env::var("CARGO_CFG_CURVE25519_DALEK_BITS").as_deref() {
         Ok("32") => DalekBits::Dalek32,
         Ok("64") => DalekBits::Dalek64,
         _ => deterministic::determine_curve25519_dalek_bits(&target_arch),
     };
-    build_debug!("CARGO_CFG_CURVE25519_DALEK_BITS: {:?}", std::env::var("CARGO_CFG_CURVE25519_DALEK_BITS").as_deref());
-    build_debug!("curve25519_dalek_bits {:?}", curve25519_dalek_bits);
 
     println!("cargo:rustc-cfg=curve25519_dalek_bits=\"{curve25519_dalek_bits}\"");
 
@@ -47,12 +50,6 @@ fn main() {
         println!("cargo:rustc-cfg=allow_unused_unsafe");
     }
 
-    let target_arch = match std::env::var("CARGO_CFG_TARGET_ARCH") {
-        Ok(arch) => arch,
-        _ => "".to_string(),
-    };
-    build_debug!("target_arch {}",target_arch);
-
     // Backend overrides / defaults
     let curve25519_dalek_backend =
         match std::env::var("CARGO_CFG_CURVE25519_DALEK_BACKEND").as_deref() {
@@ -66,25 +63,13 @@ fn main() {
                     // See: issues/532
                     false => panic!("Could not override curve25519_dalek_backend to simd"),
                 }
-            },
-            //coprocessor for Precursor
-            Ok("u32e_backend") => {
-                if curve25519_dalek_bits != DalekBits::Dalek32{
-                    panic!("u32e_backend only supports 32 bit bits");
-                }
-                "u32e_backend"
-            },
-            // default between serial / simd (if potentially capable)
-            _ => match is_precursor(platform) {
-                true => "u32e_backend",
-                false => match is_capable_simd(&target_arch, curve25519_dalek_bits) {
-                    true => "simd",
-                    false => "serial",
-                },
             }
+            // default between serial / simd (if potentially capable)
+            _ => match is_capable_simd(&target_arch, curve25519_dalek_bits) {
+                true => "simd",
+                false => "serial",
+            },
         };
-    build_debug!("CARGO_CFG_CURVE25519_DALEK_BACKEND: {:?}", std::env::var("CARGO_CFG_CURVE25519_DALEK_BACKEND").as_deref());
-    build_debug!("curve25519_dalek_backend {:?}", curve25519_dalek_backend);
     println!("cargo:rustc-cfg=curve25519_dalek_backend=\"{curve25519_dalek_backend}\"");
 }
 
@@ -92,10 +77,6 @@ fn main() {
 fn is_capable_simd(arch: &str, bits: DalekBits) -> bool {
     arch == "x86_64" && bits == DalekBits::Dalek64
 }
-// Is the target the Precursor?
-fn is_precursor(platform: &Platform) -> bool {
-    platform.target_os == target::OS::Xous && platform.target_arch == target::Arch::Riscv32
-}
 
 // Deterministic cfg(curve25519_dalek_bits) when this is not explicitly set.
 mod deterministic {
diff --git a/curve25519-dalek/src/backend/serial/u32e/constants.rs b/curve25519-dalek/src/backend/serial/u32e/constants.rs
index 2e4a5e8..d30a0fc 100644
--- a/curve25519-dalek/src/backend/serial/u32e/constants.rs
+++ b/curve25519-dalek/src/backend/serial/u32e/constants.rs
@@ -54,6 +54,7 @@ pub(crate) const SQRT_M1: Engine25519 = Engine25519([
 176, 160, 14, 74, 39, 27, 238, 196, 120, 228, 47, 173, 6, 24, 67, 47, 167, 215, 251, 61, 153, 0, 77, 43, 11, 223, 193, 79, 128, 36, 131, 43]);
 
 /// `APLUS2_OVER_FOUR` is (A+2)/4. (This is used internally within the Montgomery ladder.)
+#[allow(dead_code)]
 pub(crate) const APLUS2_OVER_FOUR: Engine25519 = Engine25519([
 66, 219, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
 
diff --git a/curve25519-dalek/src/backend/serial/u32e/mod.rs b/curve25519-dalek/src/backend/serial/u32e/mod.rs
index 64cb111..61c6b4b 100644
--- a/curve25519-dalek/src/backend/serial/u32e/mod.rs
+++ b/curve25519-dalek/src/backend/serial/u32e/mod.rs
@@ -14,7 +14,6 @@
 //! This code is intended to be portable, but it requires that
 //! multiplication of two \\(32\\)-bit values to a \\(64\\)-bit result
 //! is constant-time on the target platform.
-
 use utralib::generated::*;
 
 pub mod field;