diff --git a/src/fcmp/fcmp_rust/fcmp++.h b/src/fcmp/fcmp_rust/fcmp++.h
index ccfa2b90d..2648d3c7f 100644
--- a/src/fcmp/fcmp_rust/fcmp++.h
+++ b/src/fcmp/fcmp_rust/fcmp++.h
@@ -72,9 +72,8 @@ struct SelenePoint {
 
 // ----- End deps C bindings -----
 
-template<typename T>
 struct CResult {
-  T* value;
+  void* value;
   void* err;
 };
 
@@ -111,17 +110,12 @@ HeliosScalar helios_zero_scalar();
 
 SeleneScalar selene_zero_scalar();
 
-CResult<HeliosPoint> hash_grow_helios(HeliosPoint existing_hash,
+CResult hash_grow_helios(HeliosPoint existing_hash,
                                              uintptr_t offset,
                                              HeliosScalar existing_child_at_offset,
                                              HeliosScalarSlice new_children);
 
-CResult<HeliosPoint> hash_trim_helios(HeliosPoint existing_hash,
-                                             uintptr_t offset,
-                                             HeliosScalarSlice children,
-                                             HeliosScalar child_to_grow_back);
-
-CResult<SelenePoint> hash_grow_selene(SelenePoint existing_hash,
+CResult hash_grow_selene(SelenePoint existing_hash,
                                              uintptr_t offset,
                                              SeleneScalar existing_child_at_offset,
                                              SeleneScalarSlice new_children);
diff --git a/src/fcmp/tower_cycle.cpp b/src/fcmp/tower_cycle.cpp
index 2bf6f7459..5679a310d 100644
--- a/src/fcmp/tower_cycle.cpp
+++ b/src/fcmp/tower_cycle.cpp
@@ -51,14 +51,18 @@ Helios::Point Helios::hash_grow(
     const Helios::Scalar &existing_child_at_offset,
     const Helios::Chunk &new_children) const
 {
-    fcmp_rust::CResult<Helios::Point> result = fcmp_rust::hash_grow_helios(
+    auto result = fcmp_rust::hash_grow_helios(
         existing_hash,
         offset,
         existing_child_at_offset,
         new_children);
-    if (result.err != nullptr) {
-      throw std::runtime_error("failed to hash grow");
+
+    if (result.err != nullptr)
+    {
+        free(result.err);
+        throw std::runtime_error("failed to hash grow");
     }
+
     typename Helios::Point res;
     memcpy(&res, result.value, sizeof(typename Selene::Point));
     free(result.value);
@@ -88,14 +92,18 @@ Selene::Point Selene::hash_grow(
     const Selene::Scalar &existing_child_at_offset,
     const Selene::Chunk &new_children) const
 {
-    fcmp_rust::CResult<Selene::Point> result = fcmp_rust::hash_grow_selene(
+    auto result = fcmp_rust::hash_grow_selene(
         existing_hash,
         offset,
         existing_child_at_offset,
         new_children);
-    if (result.err != nullptr) {
-      throw std::runtime_error("failed to hash grow");
+
+    if (result.err != nullptr)
+    {
+        free(result.err);
+        throw std::runtime_error("failed to hash grow");
     }
+
     typename Selene::Point res;
     memcpy(&res, result.value, sizeof(typename Selene::Point));
     free(result.value);