diff --git a/linkerd/app/core/src/metrics.rs b/linkerd/app/core/src/metrics.rs
index baee0aa785..ffca10efca 100644
--- a/linkerd/app/core/src/metrics.rs
+++ b/linkerd/app/core/src/metrics.rs
@@ -422,7 +422,7 @@ impl FmtLabels for Class {
                 "classification=\"{}\",grpc_status=\"{}\",error=\"\"",
                 class(res.is_ok()),
                 match res {
-                    Ok(code) | Err(code) => code,
+                    Ok(code) | Err(code) => <i32>::from(*code),
                 }
             ),