diff --git a/src/HttpClient/middlewares/inflight.ts b/src/HttpClient/middlewares/inflight.ts
index 4197e010b..5b17df1d1 100644
--- a/src/HttpClient/middlewares/inflight.ts
+++ b/src/HttpClient/middlewares/inflight.ts
@@ -17,10 +17,13 @@ export const singleFlightMiddleware = async (ctx: MiddlewareContext, next: () =>
   // cancel any request
   ctx.config.cancelToken = undefined
 
-  if (!metricsAdded) {
+  // global.metrics is only initialized by startApp() in the IO service
+  // runtime. Standalone consumers of HttpClient (e.g. the toolbelt CLI)
+  // run without it, so guard the bare global reference.
+  if (!metricsAdded && typeof metrics !== 'undefined') {
     metrics.addOnFlushMetric(() => ({
       name: 'node-vtex-api-inflight-map-size',
-      size: inflight.entries.length,
+      size: inflight.size,
     }))
     metricsAdded = true
   }