diff --git a/src/fcmp/fcmp_rust/Cargo.lock b/src/fcmp/fcmp_rust/Cargo.lock
index e9c67b679..18edc208f 100644
--- a/src/fcmp/fcmp_rust/Cargo.lock
+++ b/src/fcmp/fcmp_rust/Cargo.lock
@@ -249,6 +249,7 @@ dependencies = [
  "generalized-bulletproofs",
  "helioselene",
  "rand_core",
+ "std-shims",
 ]
 
 [[package]]
diff --git a/src/fcmp/fcmp_rust/Cargo.toml b/src/fcmp/fcmp_rust/Cargo.toml
index 828cd2c2e..f4efeff9c 100644
--- a/src/fcmp/fcmp_rust/Cargo.toml
+++ b/src/fcmp/fcmp_rust/Cargo.toml
@@ -8,6 +8,8 @@ name = "fcmp_rust"
 crate-type = ["staticlib"]
 
 [dependencies]
+std-shims = { git = "https://github.com/kayabaNerve/fcmp-plus-plus" }
+
 rand_core = { version = "0.6", features = ["getrandom"] }
 
 transcript = { package = "flexible-transcript", git = "https://github.com/kayabaNerve/fcmp-plus-plus", features = ["recommended"] }
diff --git a/src/fcmp/fcmp_rust/src/lib.rs b/src/fcmp/fcmp_rust/src/lib.rs
index 16d17510b..7907e6927 100644
--- a/src/fcmp/fcmp_rust/src/lib.rs
+++ b/src/fcmp/fcmp_rust/src/lib.rs
@@ -1,4 +1,4 @@
-use std::{io, sync::OnceLock};
+use std_shims::sync::OnceLock;
 
 use rand_core::OsRng;
 
@@ -154,7 +154,7 @@ pub extern "C" fn hash_grow_helios(
     offset: usize,
     existing_child_at_offset: HeliosScalar,
     new_children: HeliosScalarSlice,
-) -> CResult<HeliosPoint, io::Error> {
+) -> CResult<HeliosPoint, ()> {
     let hash = hash_grow(
         helios_generators(),
         existing_hash,
@@ -166,7 +166,7 @@ pub extern "C" fn hash_grow_helios(
     if let Some(hash) = hash {
         CResult::ok(hash)
     } else {
-        CResult::err(io::Error::new(io::ErrorKind::Other, "failed to grow hash"))
+        CResult::err(())
     }
 }
 
@@ -201,7 +201,7 @@ pub extern "C" fn hash_grow_selene(
     offset: usize,
     existing_child_at_offset: SeleneScalar,
     new_children: SeleneScalarSlice,
-) -> CResult<SelenePoint, io::Error> {
+) -> CResult<SelenePoint, ()> {
     let hash = hash_grow(
         selene_generators(),
         existing_hash,
@@ -213,7 +213,7 @@ pub extern "C" fn hash_grow_selene(
     if let Some(hash) = hash {
         CResult::ok(hash)
     } else {
-        CResult::err(io::Error::new(io::ErrorKind::Other, "failed to grow hash"))
+        CResult::err(())
     }
 }