diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index 7aa3a60316a9..1d76eb82578c 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -495,7 +495,7 @@ fn merge_codegen_units<'tcx>(
         // If we didn't zero-pad the sorted-by-name order would be `XYZ-cgu.0`,
         // `XYZ-cgu.1`, `XYZ-cgu.10`, `XYZ-cgu.11`, ..., `XYZ-cgu.2`, etc.
         codegen_units.sort_by_key(|cgu| cmp::Reverse(cgu.size_estimate()));
-        let num_digits = codegen_units.len().ilog10() as usize + 1;
+        let num_digits = std::hint::black_box(codegen_units.len().ilog10() as usize + 1);
         for (index, cgu) in codegen_units.iter_mut().enumerate() {
             // Note: `WorkItem::short_description` depends on this name ending
             // with `-cgu.` followed by a numeric suffix. Please keep it in