diff --git a/cranelift/codegen/src/isa/zkasm/inst/emit.rs b/cranelift/codegen/src/isa/zkasm/inst/emit.rs
index 2205cd4d22ee..e7f430f3a03c 100644
--- a/cranelift/codegen/src/isa/zkasm/inst/emit.rs
+++ b/cranelift/codegen/src/isa/zkasm/inst/emit.rs
@@ -458,8 +458,7 @@ impl MachInstEmit for Inst {
             Inst::Ineg { rd, rs1 } => {
                 let rs = allocs.next(*rs1);
                 let rd = allocs.next(rd.to_reg());
-                // TODO(nagisa): this wants to conditionally use the `SUB` instruction instead (if
-                // the negation is for 64 bits)
+                // FIXME(#81): should this use a SUB?
                 put_string(
                     &format!("0n - {} => {}\n", reg_name(rs), reg_name(rd)),
                     sink,
@@ -468,12 +467,9 @@ impl MachInstEmit for Inst {
             Inst::Bnot { rd, rs1 } => {
                 let rs = allocs.next(*rs1);
                 let rd = allocs.next(rd.to_reg());
+                // FIXME(#81): should this use a SUB?
                 put_string(
-                    &format!(
-                        "18446744073709551615n - {} => {}\n",
-                        reg_name(rs),
-                        reg_name(rd)
-                    ),
+                    &format!("{}n - {} => {}\n", u64::MAX, reg_name(rs), reg_name(rd)),
                     sink,
                 );
             }
diff --git a/cranelift/codegen/src/isa/zkasm/inst/mod.rs b/cranelift/codegen/src/isa/zkasm/inst/mod.rs
index 100e9c8e975a..232904fd41ba 100644
--- a/cranelift/codegen/src/isa/zkasm/inst/mod.rs
+++ b/cranelift/codegen/src/isa/zkasm/inst/mod.rs
@@ -1025,14 +1025,14 @@ impl Inst {
             Inst::Ineg { rd, rs1 } => {
                 let rd = format_reg(rd.to_reg(), allocs);
                 let rs = format_reg(*rs1, allocs);
-                // FIXME: should this use a SUB?
+                // FIXME(#81): should this use a SUB?
                 format!("0n - {rs} => {rd}")
             }
             Inst::Bnot { rd, rs1 } => {
                 let rd = format_reg(rd.to_reg(), allocs);
                 let rs = format_reg(*rs1, allocs);
-                // FIXME: should this use a SUB?
-                format!("18446744073709551615n - {rs} => {rd}")
+                // FIXME(#81): should this use a SUB?
+                format!("{}n - {rs} => {rd}", u64::MAX)
             }
             &Inst::Load {
                 rd,