diff --git a/crates/cpu/src/rename_execute_retire.rs b/crates/cpu/src/rename_execute_retire.rs
index 4137979..f981021 100644
--- a/crates/cpu/src/rename_execute_retire.rs
+++ b/crates/cpu/src/rename_execute_retire.rs
@@ -13,7 +13,7 @@ use crate::{
         COMMON_MOP_SRC_LEN, L2RegNum, MOp, MOpDestReg, MOpRegNum, MOpTrait, PRegNum, ReadL2RegMOp,
         UnitNum, UnitOutRegNum, WriteL2RegMOp,
     },
-    next_pc::{CallStackOp, SimValueDefault},
+    next_pc::{CallStackOp, FETCH_BLOCK_ID_WIDTH, SimValueDefault},
     register::{FlagsMode, PRegFlagsPowerISA, PRegValue},
     rename_execute_retire::{
         rename_table::{RenameTable, RenameTableDebugState, RenameTableEntry, RenameTableUpdate},
@@ -42,7 +42,7 @@ pub type MOpId = UInt<{ MOP_ID_WIDTH }>;
 #[hdl(custom_debug(sim))]
 /// A &micro;Op along with the state needed for this instance of the &micro;Op.
 pub struct MOpInstance<MOp> {
-    pub fetch_block_id: UInt<8>,
+    pub fetch_block_id: UInt<{ FETCH_BLOCK_ID_WIDTH }>,
     pub id: MOpId,
     pub pc: UInt<64>,
     /// initialized to 0 by decoder, overwritten by `next_pc()`