diff --git a/src/prometheus.ts b/src/prometheus.ts
index 94790c7..60d9d6c 100644
--- a/src/prometheus.ts
+++ b/src/prometheus.ts
@@ -26,12 +26,14 @@ export class MetricsRenderer {
     private metricName(name: string): string {
         name = name.replace(/^(.*_)?(total)_(.*)$/, '$1$3_$2')
 
-        return sanitizePrometheusMetricName(
-            this.prefix.split('').reverse().join('').replace(/^_+/, '').split('').reverse().join('') + '_' + name,
-        )
+        return sanitizePrometheusMetricName(stringReverse(stringReverse(this.prefix).replace(/^_+/, '')) + '_' + name)
     }
 }
 
+function stringReverse(str: string): string {
+    return str.split('').reverse().join('')
+}
+
 const retryAfterWhileDiscovery = 15
 const textContentType = 'text/plain; charset=utf-8'
 const prometheusSpecVersion = '0.0.4'