diff --git a/src/perf/index.ts b/src/perf/index.ts
index 4c72715a44..bb5d4aba2d 100644
--- a/src/perf/index.ts
+++ b/src/perf/index.ts
@@ -118,16 +118,16 @@ export class PerfService implements Startable {
   }
 
   // measureDownloadBandwidth returns the measured bandwidth in bits per second
-  async measureDownloadBandwidth (peer: PeerId, size: bigint): Promise<number> {
+  async measureDownloadBandwidth (peer: PeerId, size: bigint) {
     const now = Date.now()
     await this.startPerfOnStream(peer, 0n, size)
-    return (8 * Number(size)) / ((Date.now() - now) / 1000)
+    return (8n * size) / BigInt((Date.now() - now) / 1000)
   }
 
   // measureUploadBandwidth returns the measured bandwidth in bit per second
   async measureUploadBandwidth (peer: PeerId, size: bigint) {
     const now = Date.now()
     await this.startPerfOnStream(peer, size, 0n)
-    return (8 * Number(size)) / ((Date.now() - now) / 1000)
+    return (8n * size) / BigInt((Date.now() - now) / 1000)
   }
 }