diff --git a/rust/rbac-registration/src/cardano/cip509/rbac/role_data.rs b/rust/rbac-registration/src/cardano/cip509/rbac/role_data.rs
index 7a46a4259b1..448a608e3f0 100644
--- a/rust/rbac-registration/src/cardano/cip509/rbac/role_data.rs
+++ b/rust/rbac-registration/src/cardano/cip509/rbac/role_data.rs
@@ -137,14 +137,14 @@ impl Decode<'_, ProblemReport> for CborRoleData {
 
 /// Decodes a signing key.
 fn decode_signing_key(
-    d: &mut Decoder, context: &str, report: &ProblemReport,
+    d: &mut Decoder, context: &str, report: &mut ProblemReport,
 ) -> Result<Option<KeyLocalRef>, ()> {
     if let Err(e) = decode_array_len(d, "RoleSigningKey") {
         report.other(&format!("{e:?}"), context);
         return Err(());
     }
 
-    match KeyLocalRef::decode(d, &mut ()) {
+    match KeyLocalRef::decode(d, report) {
         Ok(v) => Ok(Some(v)),
         Err(e) => {
             report.other(
@@ -158,14 +158,14 @@ fn decode_signing_key(
 
 /// Decodes an encryption key.
 fn decode_encryption_key(
-    d: &mut Decoder, context: &str, report: &ProblemReport,
+    d: &mut Decoder, context: &str, report: &mut ProblemReport,
 ) -> Result<Option<KeyLocalRef>, ()> {
     if let Err(e) = decode_array_len(d, "RoleEncryptionKey") {
         report.other(&format!("{e:?}"), context);
         return Err(());
     }
 
-    match KeyLocalRef::decode(d, &mut ()) {
+    match KeyLocalRef::decode(d, report) {
         Ok(v) => Ok(Some(v)),
         Err(e) => {
             report.other(
diff --git a/rust/rbac-registration/src/cardano/cip509/types/key_local_ref.rs b/rust/rbac-registration/src/cardano/cip509/types/key_local_ref.rs
index ee7b3cc03be..a05b0b10c1b 100644
--- a/rust/rbac-registration/src/cardano/cip509/types/key_local_ref.rs
+++ b/rust/rbac-registration/src/cardano/cip509/types/key_local_ref.rs
@@ -1,5 +1,6 @@
 //! A local key reference.
 
+use catalyst_types::problem_report::ProblemReport;
 use cbork_utils::decode_helper::decode_helper;
 use minicbor::{decode, Decode, Decoder};
 use strum_macros::FromRepr;
@@ -12,7 +13,7 @@ pub struct KeyLocalRef {
     /// Local reference.
     pub local_ref: LocalRefInt,
     /// Key offset.
-    pub key_offset: u64,
+    pub key_offset: usize,
 }
 
 /// Enum of local reference with its associated unsigned integer value.
@@ -27,11 +28,23 @@ pub enum LocalRefInt {
     PubKeys = Cip509RbacMetadataInt::PubKeys as u8, // 30
 }
 
-impl Decode<'_, ()> for KeyLocalRef {
-    fn decode(d: &mut Decoder, ctx: &mut ()) -> Result<Self, decode::Error> {
-        let local_ref = LocalRefInt::from_repr(decode_helper(d, "LocalRef in KeyLocalRef", ctx)?)
-            .ok_or(decode::Error::message("Invalid local reference"))?;
-        let key_offset: u64 = decode_helper(d, "KeyOffset in KeyLocalRef", ctx)?;
+impl Decode<'_, ProblemReport> for KeyLocalRef {
+    fn decode(d: &mut Decoder, report: &mut ProblemReport) -> Result<Self, decode::Error> {
+        let local_ref =
+            LocalRefInt::from_repr(decode_helper(d, "LocalRef in KeyLocalRef", &mut ())?)
+                .ok_or(decode::Error::message("Invalid local reference"))?;
+        let key_offset: u64 = decode_helper(d, "KeyOffset in KeyLocalRef", &mut ())?;
+        let key_offset = if let Ok(v) = usize::try_from(key_offset) {
+            v
+        } else {
+            report.invalid_value(
+                "key_offset",
+                &format!("{key_offset}"),
+                &format!("Value must be less than {}", usize::MAX),
+                "KeyLocalRef decoding",
+            );
+            0
+        };
         Ok(Self {
             local_ref,
             key_offset,